Fixes mistake in FilteredVideo's restore. Adds functions for saving and restoring observers to observable.
Fixes signatures of save and restore methods of observable.
Adjusts save and restore methods from my saveable observables to use the save and restore methods of observable.
Stupid Jonas forgot that observers aren't necessarily saveable... so he removes everything from tha last few commits again...
Why the hell am I in the master branch? Now really removes the broken stuff from the last commits.