Split/paver LMS-11211

@jzoldak @cpennington  Please review.
- *Acceptance Tests:*  For now, when no default_store is specified, we will not automatically test with Split, since there are failures that we'll need to debug.  One can still pass in "default_store"=split as an argument to test with Split.  All Mongo tests will still run as before.
- *BokChoy Tests:* I'm having Jenkins test the BokChoy tests since my local VM is currently screwed up.  If there are test failures specific to Split here as well, we'll disable Split for default for BokChoy as well, in this PR.  We'll open a new story or new bugs for each.
This is a different pattern than we have for the `AcceptanceTestSuite`, which uses `subsuites`. Is that intentional?