Store extensions so that they can be updated

Change-Id: I2ceb69a2bd60f0c978025315b5eb15e54933c562
Removed the import option, make open use it

Added some extra bits to the file toolbar, as well as removing the
distinction between open and import.

Change-Id: I3818a3bfc8362199169418bfc600a6304b2cd4bb
Switched the default to the EditGLWidget

When first opening up the application enable editing. We need to add
some easier/simpler logic to switch widget types (this is not very
intuitive whichever one is default in my opinion).

Ultimately we may want to generalize the widgets to store lists of
editable and "read-only" molecules, with a concept of the active one
which is the one that will be modified. This would let us more simply
switch between different modes, but it is a little more work. Sorry,
what you get here is what I have time to do in the very short term,
I think we can do much better.

Change-Id: I0b1de07961bfb689a504f2925db56dfc5010c576
Merge branch 'interface-improvements'

Change-Id: I8af721585824beb6b8e7d15230c59a64a16b8edf