Keyboard navigation/shortcuts

Copied from https://github.com/fusesource/fuseide/issues/284 .

While doing some testing, I noticed a couple of things while working in the editor. Tabbing around works great, but...

• It would be nice if you could hit the Delete key while tabbing through the Transformations list to delete a mapping.
• It would be nice if there was a shortcut for creating new fields as well in the Transformations list.
• It would be nice if you could pop up the drop-down menu in the Details view using a keyboard shortcut as well.

Definitely "nice to have" - but might be expected by keyboard users.