Change 'in' operator verbose name to sound more natural
Persist enabled flag if false, but allow validation of conditions

This prevents the circumstance when nested nodes are updated without
the language being updated. Nodes will stay-up-date, but will remain
disabled.
Move check for the enabled flag down to the parse function

If attrs are deemed _disabled_, the node itself will not be included in
the context tree. The reason for a node being disabled could be due to
an error which would cause the Node instance to be potentially unstable.
Moving the check to the parse function prevents this issue.
Fix InList to use the Exact/NotExact verbose name for one element lists