When running rb-site upgrade, the old site version is checked to see

if certain steps need to be performed. We check the display version of

the site, since that's all that we can pull from siteconfig, and

historically this has worked, with pkg_resources.parse_version()

turning this into a LegacyVersion object.
Unfortunately, this support has been dropped, causing this code path to

fail if running any beta, alpha, RC, or development releases.
To work around this, we now pull out the actual version component (the

part before a space) and compare using that.
Since pkg_resources is deprecated, this also moves our version parsing

to packaging.version.parse instead. This is the first step toward

moving away from pkg_resources.

Tested a site upgrade, verifying that this code path was being executed.

Verified that the version check worked fine on an alpha dev build.