Move music content to separate repo.
Removed old timer event classes
Merge branch 'develop' into soundtrack
Dont expose internal data in Facet interfaces
Don't crash if assets can't be reloaded/disposed properly
Dispose streaming music assets correctly
A very basic autosave mechanism.
Don't create a ModuleConfig that doesn't get saved.
Extracted createGAmeManifest and saveGameManifest methods.
Reduced autosave interval,
Simplified the creation of the GlobalStore.
Big unfinished change to save transactions:

The game takes now a snapshot on the main thread and writes it in a
background thread.

Performance isn't great yet: All chunks are encoded in the main thread.

The purgeWorld command got replaced by a save command, as the former
need to be reimplemented from scratch.

The chunk unloading has been disabled for now,
until it is ported to the new system.

Disconnecting players don't get handled properly yet, as their
state saving needs to be ported to the new system too.
Encode chunks off the main thread.
Limit the number of concurrent savings to 1.
Ported some StorageManagerInternal tests to the new API.
Make StorageManagerTest properly test the storage of zipped chunks.

It no longer extends from TerasologyTestingEnvironment as the creation
of the zip file system doesn't work ontop of a fake file system.
Simplified some StorageManagerTests by doing more in the test setup method.
Port the remaining StorageManagerTests to the new API.
Ported the chunk unloading to the new save system.
Don't stop the ChunkProvider as it can run concurrent with save snapshot creation.