scide: fill command line from shortcut

using Ctrl+Shift+E, one can now fill a command line from the current
selection.

Signed-off-by: Tim Blechmann <tim@klingt.org>
scide: avoid some duplicate code

Signed-off-by: Tim Blechmann <tim@klingt.org>
Merge pull request #711 from timblechmann/topic/ide_cmdline