recursively stores fingerprint for @import'ed css
Merge branch '1.6.x' into gi108
small tweaks on contributed code
use org.junit package
get rid of duplicated code
rename a method and add javadoc
Incremental build must build only resources under it's own <targetGroups>

Added a check to filter out resources external to <targetGroups>
Merge remote-tracking branch 'gonzalad/issue110' into i108
remove unused variable. Still have to creat unit tests
improve logging on errors
fix failing unit tests
create test which proves that incremental change is not detected for a non target group
fix merge conflicts