Patches: focus_nth, bring, win titles in completion

[Gabor Adam Toth <tg _at_ tgbit _dot_ net>]

Hi,

the following patches add two new commands:

- focus_nth: focus nth window in current frame
- bring: move a window to current frame

Another patch adds window titles to the WINID completion list, and the last
patch allows the herbstcommander script to take a partial herbstclient command
as the starting point for completion. With this change a key binding can be
added for the bring command like this:
hc keybind $Mod-b spawn herbstcommander bring

-tg