Remove unused code.
Do not rely on the url scheme owncloud(s) any more.

If it is not owncloud or ownclouds, rely on the scheme
that was given by the user.
Revert "Do not rely on the url scheme owncloud(s) any more."

This reverts commit 34dd3b207ed139a4f3e2cc1578e9afc7916977bb.
It can be implemented simpler.
Also allow http and https protocols.
Make it an error instead of a crash when dav_connect fails.

Fixes #1591
owncloudcmd:  Fix an error during update phase would not terminate

the QApplication::quit()  would be run before the exec() and would
be a noop,   and then exec would just wait forever.
Merge branch '1.5'

Conflicts:
	src/owncloudcmd/owncloudcmd.cpp