Input type on creation and switching between input types

[chkworks]

Currently there are three main input types for keyframes and clips - “Constant Value”, “Live Value” and Layer. I was asking myself if the “Create” menu give the concept of Layer and Composition a bit more weight, by not including them in the keyframe menu. In the workshop you were mainly talking about both types as functions, so I think it helps mentally to isolate them from the concept of keyframes.

Also it would be nice to anytime switch between a Constant and a Live Value, maybe in the Inspector and also possibly via a context menu. I think it would make sense to simply double-click into the timeline and then change the type to “Live” in the Inspector. Probably related to #264