[Editor] Don't display completion box when inserting external text

Sometimes, the completion popup is shown after clicking on a formula from the
formula book, or inserting a variable from the variables dock.

This is a re-fix of an old issue:
http://code.google.com/p/speedcrunch/issues/detail?id=173
[MainWindow] Assign new shortcuts for switching result format

http://code.google.com/p/speedcrunch/issues/detail?id=344