New icon sets for gui's floating widgets

[Torsten]

Hi all,

as a result of discussion

http://octave.1599824.n4.nabble.com/icons-of-floating-widgets-in-gui-td4645883.html
(thanks Dan!) I implemented two different icon sets for the gui's
floating widgets with changeset
  http://hg.savannah.gnu.org/hgweb/octave/rev/b081fbe80174
The icons are based on the ocatve logo (easy assignment to octave)
extended by a graphic or a letter related to the specific widget
(editor, history etc.). The settings dialog provides a possibility to
chose between no icon (just the octave logo), the letter- or the
graphic-logos. The graphic logos may need some further polishing.

We should decide which icon set is suitable (if any) or if both sets
should remain leaving the choice to the user.

Torsten