Beefed  upDeltaApplicationVisitorFixture, puttered

- added series of tests to DAVF, still need to consider testing visitors
- cleaned up some using statements
- found more bugs in visitor implementation, cleaned those out. Involves
exposing something nasty through IVersionControlNode, something that
should really be internal to the class.
- put some warnings on the IVersionControlNode interface for later
investigation.
- tidied up versioning list
- pushed resharper preferences into file, will see if the propagate to
laptop.
- further moved "handy-to-have" methods from List to List extension
methods.
- played around with ICloneable, came up with something not atrocious.