Use full URI for android application Gradle plugin
Remove useless include from Gradle settings
Move submodules back to libs/
Add some logic for signing releases
Update otr4j to 0.21
Pull otr4j form Maven repo
Add non-project files back
Use proguard on release builds

We don't need obfuscation (it's an open source project), but proguard
wil shrink the apk by stripping out unused code.
Suppress lint errors and remove bcprov
Add proguard rules
Make conversations the root project
Add build deps and move build props to build file
Add gradle directory
Use Gradle build system