Shortcut conversion in FileBrowser

As of r1944 it is possible again to set shortcuts with prepended event names, e.g.
“keyup:ctrl+s” (keyup, kedown or keypress are valid event names). In the file browser,
shortcuts are converted to be used with ace. The new shortcut format should be applied
in this conversion function.

(from redmine: issue id 2159, created on 2015-03-03 by root, closed on 2015-03-03)

• Changesets:
  • Revision 1977 by Thorben Quast on 2015-03-03T15:30:51Z:

fix #2159

• Revision 1977 by Thorben Quast on 2015-03-03T15:30:51Z:

fix #2159