Improvements and cleanup for 0.7-SNAPSHOT

  * Version bump and lots of comments
  * New plugin structure using configurations
  * New Proguard rules, automatic generation (aapt -G)
  * Ability to use a custom Proguard configuration file
  * Easier classpath management
  * Easier preloading, with support for arbitrary libraries
  * Many fixes (ApkLibs, test projects,...)
  * Device-specific commands don't exist anymore, use adbTarget
  * Setting for the default IntelliJ configuration
  * Fixed old "market" terminology
[fix] Fixed default keyalias missing
[fix] "apk" and "release" delegates in Global
[fix] Fixed "release" in Global scope
[feature] Preliminary AAR library support
[feature] Typed resource on/off flag
[fix] Include apklibs from unmanagedBase
[fix] NPE when filtering non-existing unmanagedBase
[feature] Settings for standard Ant projects
[fix] No lib/ created if it doesn't exist
[fix] Don't generate TR if useTR is false
[fix] "empty.reduceLeft" error when no buildTools
[fix] Wrong Google resolver URI on Windows
[cleanup] nativeLibrariesPath key name more consistent
[fix] nativeLibrariesPath in Global scope
[feature] Rewritten NDK settings
[fix] Removed androidNdk key (useless now)
[cleanup] aaptGenerate now much cleaner
[fix] Use the Gradle convention for libs/lib

  * libs/ for JAR libraries
  * lib/ for native libraries
[fix] mpeltonen/sbt-idea#238