new emoji drawer

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Closes #1746
Null check for cipher text to prevent NPE on decryption

Fixes #1703
Closes #1728
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Move default SMS and system import to "reminders"

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Closes #1730
Update BUILDING.md

Correction of a typo and a few style incongruences.

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Closes #1750
Fix emoji backwards compatibility recents crash

The old emoji drawer stored emoji with a .png suffix. Replace it during
list deserialization.
Add a backspace key to the emoji drawer
Remove gray placeholder squares while loading emoji
Occupy all vertical space for emoji grid

Fixes the recent emoji list leaving an empty gap at the bottom of the
drawer depending on the number of items shown.
Whoops, add GcmRegistrationService to Manifest.

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Updated language translations.

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Bumping version to 2.1.2

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Can't toast on this thread.

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Bump version to 2.1.3

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don't use old emoji recents, broken

Fixes #1782
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make reminder a custom view, make push reminder

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fix unused argument

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fix EmojiLRU concurrency exception

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Bump version to 2.1.4

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transport selection rewrite

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