This commit include lots of changes for pose editor.
Before, we use buttons to represent the transform controller for bones;
Now, we use nodes and edges to represent the bones, just like the nodes and edges for representing the guide spheres for mesh generating. There are advantages by doing this. Firstly, The edit UI for both mesh and pose are unified, secondly, it is possible to set a reference sheet for pose editing now, this is very important.
This new pose editor is inspired by the Eadweard Muybridge's work.
Shortcuts implementation now use QShortcut instead of using the raw key event.
Besides, hold spacebar to temporarily enter drag mode also implemented in this commit, this is very useful in zoom mode.
Jeremy Hu