Filter animated parameters

[pgilfernandez]

Sometimes, as commented in #655 (comment), navigating the timeline looking for your animated parameters (so that you can switch to graph mode or just because you want to tweak their timing) turns a slow process as there are too many collapsible groups and the animated parameter could be buried under lots of "collapsed groups".

With this PR I used the timeline filter feature to filter parameters analyzing if they are animated or not and doing it in 2 ways:

• without removing their hierarchy
• removing their whole hierarchy by just exposing the parameter

There is still some work to do if we decide to merge it (it can be indeed done in the future):

• create new "Parameter" filters for just exposing Transforms, effects, etc...
• assign shortcuts to the filters for fasters switching
• make filters state permanent in the document (not sure about it...)
• ...