When the user enters a private conversation after adding her second
contact, an onboarding screen will be shown highlighting the possibility
of introducing the contacts to each other.

Add functionality to save and restore recently used Emojis

Update emoji and add new categories based on AOSP's XML file

Closes #593

Also replace more raster graphics with vector graphics.

Closes #342

Closes #429

Closes #517

This commit addes a combined blog feed that shows all posts of all
subscribed blogs in the order the blog posts have been received.

For now, this commit also hides other blog functionality like adding
additional blogs and browsing individual blogs.

Closes #417

This implements a generic `TrustIndicatorView` with a `setTrustLevel()`
method which updates the drawable according to the `Author.State`.

Closes #78

This replaces the custom layouts in the navigation drawer with a
`NavigationView` and adds a menu entry for Blogs.

A Main Blogs fragment is added that holds a `TabLayout` and a
`ViewPager`. Five tabs are already added, but they just have a single
placeholder fragment that is to be replaced by the actual fragments.

Closes #409

It does so by extending the compound view `TextAvatarView` and provides
convienient setters that take care of the required UI changes.
The new badge can also be used to indicate a problem with the forum.

Closes #408

Closes #399

Includes parallel improvements to Bluetooth key exchange UI.

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

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

Closes #313

Show system notification for successful introductions

The button hides itself when you scroll down the list of contacts
and shows again when you scroll up.

To properly color the button, the accent color has been defined.
It uses the same color as the action bar (primary color).
I leave it to a UX designer to adapt the color scheme.

Please note that the design support library was used.
It includes the app-compat library, so this has been removed
from the `build.gradle` file.

Closes #199

It now uses conversation bubbles in alternating colors
and vector drawables to indicate message state.

The conversation bubbles have been taken from Telegram
and can be replaced by a UX designer later.

This commit also addresses #9, because message text can
now be selected and copied. This is done by using

    android:textIsSelectable="true"

which only works for API level 11 or higher.

If we want copy and paste on lower API levels,
additional measures have to be implemented.

Closes #179

and indicate which transports are currently available.
The icons have been chosen from the official material icons and might be
replaced later with icons that better represent the given transport.

Please note that I used vector drawables which will be automatically
converted at build time to raster graphics.

Closes #96

UI was transferred into XML files
and lots of redundant code was deleted such as the custom CodeEntryView.

Closes #33

Users were confused by the process of adding a contact for the first time.
This change adds additional explanation and a picture of what is going on.

It also moves part of the UI into XML files.

Closes #87