* lib/versioner: Factor out DefaultPath constant.
Replace several instances where .stversions is named literally to all
use the same definition in the versioner package. Exceptions are the
packages where a cyclic dependency on versioner is impossible, or some
tests which combine the versions base path with other components.
* lib/versioner: Fix comment about trash can in simple versioner.
* lib/versioner: Fix wrong versioning type string in error message.
The error message shows the folder type instead of the versioning
type, although the correct field is used in the comparison.