since the entire ting is so incredibly broken in cmake,
use the approach taken by csync (which emulates the
approach of autotools), to get the directories right.
This mandates changes in the theme, which need discussion
(APPLICATION_SHORTNAME must now equal appName(), and
APPLICATION_NAME should equal appGuiName()).
This implements out-of-repository-theming, and removes the old
custom.ini theming that never worked on all platforms and had
no straight deployment story.
The new approach requires the CMAKE variable OEM_THEME_DIR to
point to a directory that must at least contain an OEM.cmake file
(check OWNCLOUD.cmake for possible options) as well as a themes.qrc
and a themes/ directory that directly correspond to the ones in
the source tree.
