Changed project structure and IDE from Eclipse to Android Studio

Notes:
Create debug and release builds by "gradlew clean && gradlew --offline build"
Before release specify signing config in "signing.properties" locally or on build server

Changes:
Raised targetSdk to 21 (LOLLIPOP), implemented App Bar (formerly ActionBar)
Black and red theme for main activity, otherwise default dark
New icon following Material Design guidelines
Server address preference hidden in release build
Separated logic from activities to fragments
"Dim screen" button in menu, auto dim system UI