Allow commandline arguments for windowmanager setting

This fix gives the option to specify startup arumgents
for the windowmanager setting.
Merge branch 'master' of git://github.com/nebulon1234/razor-qt (#552)
fixed #550 Wallpaper not centered, Color does not fill whole BG
Merge remote-tracking branch 'upstream/master'
Fixed #538 razor-panel: Restore (a minimized window) is not working while using Fluxb
ignored duplicate entries in the HistoryProvider

Currently razorqt-runner can produce duplicates in the history:
if you run the same command from the CustomCommandProvider twice, it
will be inserted into the HistoryProvider-list and the file twice.

This patch checks changes HistoryProvider::AddCommand, so that it will
search if this command already exists and it will move that entry to
the top of the list (instead of creating a new item).
Merge branch 'master' of git://github.com/Boris-de/razor-qt (#556)
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of github.com:CaledoniaProject/razor-qt