Check for empty values in esxnode/storagecluster

This is intended for handling the case that a configuration value in a
configuration file includes the key, but has no value. If we don't check
for this, the alternate code path will never be executed.
Cast enum value to String before checking for validity
Invert storage cluster sorting yet again.

I just can't wrap my head around the -1/0/1 logic of Comparators -_-
Bump version, update changelog
Merge branch 'hotfix/0.4.1'