Add new property "saveDownloadedFiles"
-Create a new download directory.
-Used at LauncherUpdater and GameDownloader
-First part of #202
Add "downloadDirectory" and "saveDownloadedFiles" to SettingsMenu
Fixes #202
 Add a fallback for missing language translations
 Fixes #206
Add "Jenkins" postfix to methods of DownloadUtils
Update checkstyle.xml
#205
Add new checkstyle modules
#205
Fix some warnings (FindBugs, Checkstyle)
Fix some warnings (FindBugs, Checkstyle)
Fix some warnings (FindBugs, Checkstyle)
Fix some warnings (Checkstyle)
Fix some warnings (Checkstyle)
 Better handling for failed or change-less builds
 Fixes #207
Polish translation
Polish translation

Added and edited all necessary files.
Merge polish translation

Close #212
Close #211
Fix LabelsBundle and MessageBundle
Little fix for showing successful state
#207
 Optimize adding new translations
 Fixes #215
Update CHANGELOG.md