- Removing unused information (names and descriptions) from the Emoji class
- Creating a Gradle task that generates a more efficient res/raw/emojis.txt file from the most recent Unicode standard
- Saving recently used emoji preferences as emoji values rather than names
- Migrating old user preferences to the new system

The measurement function was wrong in some situations. Set a width for
columns and properly configure the GridView.

The class has a complicated internal logic, it is no longer reasonable
to extend it.

The meaning of the public fields of KeyValue was quite complicated and
not handled consistently accross the app.

Make these fields private and add a more abstract API on top.

The meaning of these fields changed recently and it wasn't an easy
change. I plan on making more changes in the future.

KeyValue defines an ADT and some of its values, it now contains public
final fields and no internal logic.
KeyModifier handles modifiers and accents and creates new instances of
KeyValue when needed.
This operation is now properly cached.

Take the list from https://unicode.org/Public/emoji/13.1/emoji-test.txt
Also change the list of groups, from the same source.