Vine refactor

[augustearth]

The Vine, CachingVine, and VineMethod classes/interfaces/traits are muddled.... Clean things up.

• [x] Move the basic call() mechanism from CachingVine to Vine. Currently all Vine has are static methods. The mechanism to call VineMethods (without caching) should be in Vine, so there is some meaning/benefit to extending the Vine class.
• [x] Override the Vine call() method to hook into the caching machinery. Keeping CachingVine as a trait probably makes sense, so it can be added to the man branches of Vine subclasses as needed.
• [x] Evaluate potential changes to VineMethod... Maybe it's ok to stay how it is for now.

[augustearth]

So, on closer inspection, the vine infrastructure could benefit from a more extensive refactor. The following seems true:

• The two valuable aspects of the Vine machinery are caching and H2.
• Caching does not make obvious sense for H2 file vines.
• FileVines on their own are pretty useless.
• The VineMethod interface is really only necessary to enable caching and is otherwise a pain.
• There does not seem to be a good argument to have a top level Vine class or interface that would cover all vines, though there are families of related vines.

Do the following:

• [ ] Get rid of Vine.
• [ ] Make CachingVine a top level class to replace Vine.
• [ ] Make H2FileVine a top level class.
• [ ] Remove caching from H2FileVine.
• [ ] Rename VineMethod to CachingVineMethod to make it clear where it applies.

[augustearth]

Closing this issue. Further discussion is required. Will copy the material here to the Team discussion.