#62 root context menu

[Stan Birchfield]

Right click anywhere in a root should bring up a context menu. Items in the menu should include:
- change status from live to dead and vice versa
- change color
- add point
- delete point
- etc.

Note that one or both of add/delete point should be grayed out depending on location of mouse.

Note that there is already a context menu for add/delete point. This should be folded into above behavior.

[Stan Birchfield]

Note that this needs to work for 'dead roots', too, so that the user can change them to live. Changing dead root to live will change its status in all intervening sessions.