Added a fall-back for loading FXML files.

* prevents the launcher to crash whenever a label translation is missing (for labels directly used within the FXML file)
Merge pull request #300 from skaldarnar/javafx_cleanup

Added a fall-back for loading FXML files.
Aggregate changelogs from previous builds.

* added aggregated change logs to `TerasologyGameVersions`
* default is a lookback value of 1 for stable builds and 10 for nightly builds (hard-coded, not changeable yet)

Fixes #241
Cleaned-up `getAggregateChangeLog`.