Merge branch 'feature-loadingscreen' into 'devel'

android/AndroidManifest.xml

android/assets/gfx/launch_de.png

android/assets/gfx/login_de.png

android/assets/gfx/login_sk.png

...rc/main/java/cz/nic/tablexia/android/AndroidLauncher.java

core/src/cz/nic/tablexia/Tablexia.java

core/src/cz/nic/tablexia/loader/zip/ZipAssetLoader.java

core/src/cz/nic/tablexia/screen/loader/LoaderScreen.java

.../src/cz/nic/tablexia/sync/RestSynchronizationService.java

desktop/src/cz/nic/tablexia/desktop/DesktopLauncher.java

ios/src/cz/nic/tablexia/IOSLauncher.java