Add support to ignore local variables

[ptrckkk]

This is not really an issue but more an idea how the project could be enhanced in the future.
Assumes we have a class c that is annotated with Undoable. We now have two objects, o1 and o2 of type c but want only changes for o1 to be tracked.
We can achieve this by annotating o2 with a (I propose) ObjectNotUndoable annotation.

I created a branch, preparations-issue-1, containing this annotation. The problem is how to determine if a local variable is annotated with a particular annotation. It seems that with Java's default reflective capabilities this is not possible.
If I am wrong and someone knows a way, please let me know (you will find contact data in the README file).