Add Menu, MenuBar and MenuItem widgets

[prock-fife]

These widgets would allow for easy menu generation. The fife editor would benefit by having a menu bar. It would also enable the easy addition of context menus when right clicking.

[helios2000]

Additional a Tooltip would be great.

[jakoch]

TODO

• add menu
• add menubar
• add menuitem
• add tooltip
  • onHover
• modal stack mapping (push, pop, clear)