This commit changes the manifest to do not check for too low versions
and does not download and unpack a tarball if available if the parameter
--install-only is set. This should make it useable now.
Also, a short message change to match the manual.
This type should work, but there are still many things to do here to
work nice and well.
Things that currently not work (well):
- not all parameters work for now
- nextcloud installations in subfolders (e.g. slashes in the object id)
