Create a Curve25519 asymmetric master secret for users without.

Fixes #1701
Bumping version to 2.1.1
Upgrade to new GCM API.
disable passphrase creation on registration

// FREEBIE
Closes #1726
new emoji drawer

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

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

// FREEBIE
Closes #1730
Update BUILDING.md

Correction of a typo and a few style incongruences.

// FREEBIE
Closes #1750