postmarketos-ui-i3wm (#1225)

* Added a ui package for i3wm

* Added n900 specific i3wm config

* Fixed mixed tabs and spaces in i3status.

This is also the first commit made on an n900
running postmarketOS.

* Removed redundant X11

* Use lock.sh to lock the device

* Windows management improvements

* bump pkgver

* Fix device-nokia-n900 checksums

* Fixed path in the i3wm split package