Add contact and transport keys in the same transaction

This avoids a potential problem where the app crashes after adding the contact but before adding the transport keys, leaving the contact unusable.

See merge request !112

Convert BDF types in lists and dictionaries



See merge request !111

This avoids a potential problem where the app crashes after adding the contact but before adding the transport keys, leaving the contact unusable.

New polling logic for Tor. #250

Poll for outgoing connections each time the network is enabled, then disable polling once our hidden service descriptor has been published. If our contacts do the same, any contacts that are offline when we poll will connect to us when they come online.

This should reduce bandwidth and battery usage. The idea comes from Ricochet:

https://github.com/ricochet-im/ricochet/issues/68

Fixes #250.

See merge request !103

If two contacts publish their descriptors simultaneously, they may both stop polling without retrieving each other's descriptors. Continue polling for 2 intervals after publishing the descriptor.

Poll for outgoing connections each time the network is enabled, then disable polling once our hidden service descriptor has been published.

New polling logic for LAN. #252

Same approach as !104. Modified the poller to cancel any scheduled poll when pollNow() is called and randomise the next polling interval so plugins that call pollNow() at the same time don't end up polling in sync.

Depends on !104. Fixes #252.

See merge request !105

New polling logic for Bluetooth. #251

Increase the polling interval exponentially each time polling is unsuccessful, up to a maximum of 60 minutes. The interval is reset to 2 minutes whenever a connection is made and whenever Bluetooth is re-enabled.

This should reduce battery usage when there are no contacts nearby.

Fixes #251.

See merge request !104

Try to use the real Bluetooth address on Android 6. #225

Fixes #225 until Google breaks the Settings.Secure workaround.

See merge request !109

Don't reschedule the same TimerTask. #254

Also added some unit tests for TransportKeyManager (part of #205). Fixes #254.

See merge request !108

Same exponential backoff approach as Bluetooth.

The polling interval increases exponentially each time polling is unsuccessful, up to a maximum of 60 minutes. The interval is reset to 2 minutes whenever a connection is made and whenever Bluetooth is re-enabled.

Move UniqueId comparator to Bytes for reuse



See merge request !107

Don't communicate with inactive contacts

When we're introduced to a new contact, we need to store the transport keys and start key rotation before activating the contact. During this period we shouldn't use the transport keys for outgoing streams until either the introduction protocol is complete or we receive an incoming stream from the contact, indicating that they've also started key rotation.

See merge request !106

Database efficiency improvements

Some tweaks to the DB schema to improve efficiency:

* Only keep status rows for messages that are visible - this saves space and avoids the need to join the groupVisibilities table when selecting messages to offer or send
* Use adjacent columns for the composite primary key on the settings table

This MR depends on !101.

See merge request !102

Don't keep message status rows for groups that are invisible to the contact - this avoids the need to join the groupVisibilities table when selecting messages to offer or send. Add or remove status rows when group visibility changes.

Transactions for clients

This patch moves transactions out of the database component, allowing clients to perform multiple database calls in a single transaction. This should improve efficiency and reliability, at the cost of increased boilerplate for database calls.

Operations that allow hooks, such as adding and removing contacts, pass their transactions to their hooks. This ensures the whole operation is atomic and isolated, so StorageStatus is no longer needed, hooks don't need to be idempotent, and locks can be removed from clients that were using them for isolation.

This merge request is marked WIP because it will conflict with !74.

See merge request !101

Increase contrast between identicons and background

Identicons currently have a dark or light background depending on the V component of the foreground colour. But V isn't a great measure of brightness - cyan looks much brighter than blue with the same V, for example. This leads to some identicons having low contrast between the foreground and background.

This patch scales the R, G and B components of the foreground colour to 3/4 of the full range and sets the background to white, so there's always good contrast between the foreground and background. The patch also adds a 1dp outline around identicons and adds some padding to the identity selection dropdown.

Before:
![device-2016-02-10-150200](/uploads/2456ff047d4d33b4537f3489c9018679/device-2016-02-10-150200.png)

After:
![device-2016-02-10-154634](/uploads/758c71e3c160e0f9fc50a507323daa7f/device-2016-02-10-154634.png)


See merge request !100

Psycho killer, qu'est-ce que c'est?