Update gitignore
Add Android tests
Build separate artifacts for Android and web based applications

Core differential synchronization functionality is contained in two
artifacts. 'spring-sync-core' has dependencies on Spring Framework and
is suitable for standard JVM environments, while
'spring-sync-core-android' depends on Spring for Android and is
suitable for Android apps. 'spring-sync-web' contains features for
configuring differential sync within Spring MVC.