[Downloader] Implemented first version of GUI-Downloader connection
[Downloader] Show error information in GUI
[Build] Improved generated manifest files
[Downloader] Improved launcher
[Downloader] Disable buttons while application is launched
[Downloader] Added application icon
[Downloader] Updated version of the gradle build for the downloader
[Nifty-Controls] Fixed references to changed API in Nifty-GUI
[Build] Changed source compatibility from 1.6 to 1.7
[Engine-libGDX] Updated libGDX

Updated libGDX from 0.9.9-SNAPSHOT to 0.9.9
Fixed changed API
Changed source maven repository from badlogic nightlies to oss sonatype
[Build] Set the encoding of the java files
[Build] Trigger JFX deploying along with the publishing task
[Build] Fixed typo in definition of distribution directory
[Build] Copy the downloader distribution after the build
[Build] Removed illegal access to distribution directory
[Build] Fixed distribution of the downloader
[Downloader] Fix design of empty progress bar