update version keys to something more planned

first_version and version_regexp clearly just "evolved"; so let's try to rig
something more regular via a sort of gitconfig-like dot namespacing:

    version.first
    version.regexp
    etc, etc

Hopefully this will allow us to keep things somewhat predictable :)
add repo_root attribute to our store...

...well, a temporary setup, at least.  This might need to be run through the
config settings...
details...  stash_named(), not get_stash_named()