Change the window background system-wide

This also sneaks in some small UI modifications desired by @Megalox.

Closes #307

See merge request !157

Remove old user feedback activity

Fixes #336.

See merge request !162

Don't allow 'this' to escape the constructor

Fixes #325.

See merge request !155

Implement encrypted feedback

Closes #124.

See merge request !138

Closes #307

Migrate crash reports to ACRA

Closes #123.

See merge request !140

Converts the splash screen to XML format

Removes all programatic calls that modify the layout and uses the XML
resource instead.

See merge request !123

Refactor `ContactListAdapter` to be used for Introductions and Forum Sharing

This MR introduces an abstract `BaseContactListAdapter` which provides
most of the adapter logic. The original `ContactListAdapter` extends it to
show date and online status of the contacts.

The new `ContactChooserAdapter` which is used for introductions extends
the `ContactListAdapter` and adds logic for graying out contacts from
different identities than the currently used one.

A new `ContactSelectorAdapter` extends the `BaseContactListAdapter` and
allows to select multiple contacts. It offers a method to return a
collection of all selected `ContactId`s.

Closes #292

See merge request !151

This commit introduces an abstract `BaseContactListAdapter` which provides
most of the adapter logic. The original `ContactListAdapter` extends it to
show date and online status of the contacts.

The new `ContactChooserAdapter` which is used for introductions extends
the `ContactListAdapter` and adds logic for graying out contacts from
different identities than the currently used one.

A new `ContactSelectorAdapter` extends the `BaseContactListAdapter` and
allows to select multiple contacts. It offers a method to return a
collection of all selected `ContactId`s.

This commit also sneaks in an animation when the 'Share Forum' button
is clicked.

Closes #292

Removes all programatic calls that modify the layout and uses the XML
resource instead.

Don't connect to inactive contacts

Two changes:

1. Don't use remote transport properties for contacts that are in the process of being introduced - this avoids wasted connection attempts, as we can't create stream contexts for such contacts.

2. Don't activate contacts when receiving incoming streams - doing so was meant as a workaround for newly introduced contacts having inconsistent views of their introduction status if the introducer was offline. But it just shifted the inconsistency elsewhee, so this change removes the workaround.


See merge request !153

Use consistent styling for dialogs. #296

Converted all dialogs to use the support library and the Briar theme, so they have a consistent Material Design appearance across all Android versions.

See merge request !152

This avoids wasted connection attempts to contacts that are in the process of being introduced.

This leaves the contact and the introduction session in inconsistent states.

Move create forum post and share forum buttons in action bar

According to the designs in #305, the 'create forum post' and 'share forum' buttons will go into the in action bar.

In the spirit of keeping MRs small and to avoid conflicts with #306, I did this first and independently of future work.

This also introduces constants for the `GROUP_ID`, `FORUM_NAME` and `MIN_TIMESTAMP` as they were used for the two buttons.

Closes #313

See merge request !150

Remove avatar code and layout from ConversationActivity and ConversationAdapter

Please note that I have not been able to test this MR on an actual device as I have none at the moment :(

Closes #293

See merge request !148

Show relevant introduction decline responses in the conversation

* If the user has already declined, we don't show that the other
  introducee has declined as well. The backend doesn't have that information, so
  this is compatible with the principle of showing what we know.
* If the user has already accepted or hasn't yet responded, we now show the
  decline response in the private conversation with the introducer. If
  the user hasn't yet responded, we hide the accept/decline buttons
  in the introduction request message.

Please note that I do not have three devices at the moment to test this MR in its entirety in practice. I created another test which is hopefully sufficient to ensure that the modifications are correct.

Closes #295 

See merge request !149

Encrypted crash reports

Part of #123.

See merge request !128

This also introduces constants for the GROUP_ID, FORUM_NAME and
MIN_TIMESTAMP as they were used for the two buttons.

Closes #313