Reorganize the undo_redo in core folder.
Undo/Redo when update paramDouble.
Undo/redo for the paramInt.
Fix default value for the paramInt.
Merge branch 'develop' of github.com:buttleofx/ButtleOFX into develop

Conflicts:
	buttleofx/core/graph/graph.py
	buttleofx/core/undo_redo/commands/__init__.py

Also move the cmdCreateReaderNode in core/undo_redo/commands/node.