Can install_twisted_reactor() outside of App.build
Deeper uninstall of Twisted Reactor
Allow cycles of install/uninstall of Twisted Reactor
Oops: forgot to be public about the new entry
Better docs on uninstall_twisted_reactor()
Clean unused import
Updated versionadded:: to 1.8.1
Added save_image method to Widget
Revert "Added index method to InstructionGroup"

This reverts commit cc9af2bb191338f31225c192df9739a28e29f197.

This commit only duplicates the functionality of
InstructionGroup.indexof.
Revert "Added index method to InstructionGroup"

This reverts commit cc9af2bb191338f31225c192df9739a28e29f197.
Changed save_image -> export_to_png plus bugfixes
Adding enforcement of the wanted graphics system GL/GLES
- GRAPHICS=GL/GLES
- promoted exit_on_escape functionality to BaseWindow and implemented a
  callback for it
- PEP8 fixes
prelim focus behavior.
Add docs, provide link function, add overwrite in autopopulate, fixup.
Add focus behavior example to examples.
Add to de-focus on escape.
Remove autopopulate, instead walk the tree dynamically to find next/previous focus if not specified in focus_next/previous.
Update the example to reflect changes.