ENG-6082: Damn cowboy boots...let the cluster decide whether or not a
selector is invalid, stop pre-filtering things.
ENG-6082: Some cleanup, remove the use of the project.xml from a test.
ENG-6082: Add CLASSES selector to @SystemCatalog, which will return a
list of all of the classes in the currently running catalog, along
with flags indicating whether or not each class is a potential
(subclass of) VoltProcedure, and, if so, whether or not it is an
actively installed VoltProcedure.
ENG-6082: Make sqlcmd support show classes in the worst possible way.
Make list and show aliases for each other while we're here.
ENG-6082: Address review comments: be less dumb about superclass
detection.
Merge pull request #1534 from VoltDB/eng6082

Eng6082: Add CLASSES selector to @SystemCatalog, which will return a list of all of the classes in the currently running catalog, along with flags indicating whether or not each class is a potential
(subclass of) VoltProcedure, and, if so, whether or not it is an actively installed VoltProcedure.
- Add 'show classes' command to sqlcmd which uses the new selector and semi-pretty-prints the results.
r=jhugg