DC: add clean and create scripts to make my life easier

Change-Id: I057d49dcc4903d974a16b05a6b22cc0f7df9c70d
DC: add rename build.gradle to build.gradle.default and ignore build.gradle

Change-Id: Ifeb1c393d6d149554d5e06854dfd0070603e9542
DC: update build.gradle and proguard flags, fix possible NPE

Change-Id: I92b586885ddd8e7a71f634ee6a87c18478d42fa9
version: 0.3.2

Change-Id: I317a2b7808fe21ea9af41d8b4191cb574d9ab375