Support rich text controls in input method interface

Meegotouch uses rich text controls on the input method server. These include buttons for bold, underline and italic. So far the buttons trigger ctrl+key shortcuts that just happen to be properly handled on the widget. A better mechanism for this would be nice to have.

An IM event was suggested where default implementation would send the default shortcuts. Another possibility would be extending with formatting that should apply after committing a word. Latter would have benefits with preedit injection as in QTBUG-15549.

Also related: additional commands, our rich text entry creates a font dialog when ctrl+f is received. We have a button for that also. Cut/copy/paste commands needs some support, too.

The 'cost' of not having this means it's not possible to override what ctrl-C, ctrl-V does because that's the only way to implement it.