Adding icons and manifest
Large batch of tweaks and fixes

- the window now uses ScrolledComposite instead of a regular Composite
with a slider rigged to scroll it, much more smooth
- fixed an issue that would prevent FTL from running correctly (the
executable would be started in the manager's working directory,
preventing relative paths from working corretly)
- modified options window to look better
- added drag-and-drop to add mods to the manager
- removed mergeList functionality - will be replaced with
gmm:blueprintListAppend
- changed the logger so that it is configured programmatically instead
of an external config file