More cleanup:
- Fix two slowNightly tests by removing an undefined function call (my
  bad). Move another to the regular suite since it only takes a few
  seconds.
- Make members of the Database class private, addressing a long-standing
  TODO.
- Fix a bug in building secondary indexes with uniquness checks.
- Remove some old storage artifacts for flushing files / committing
  journal on shutdown.
closes #179, make a command to propogate slave location through the GhostSync as opposed to using
a cursor. The benefit is that a command never hangs on a tailing cursor, thereby blocking the GhostSync
from processing other slaves. A concern would be buffering of data to ensure we don't send too many
commands, but the originating command will be the result of a cursor query, so the buffering ought
to be intact
change some sharding internal commands to be OPLOCK, closes #197
Check if the loader was successfully created before closing
Move a test to the regular jstests directory, it's very fast.
refs #115 sharding_migrate_cursor1.js passes for me in 87 seconds
also, fix 6155_drop_pk.js to be less paranoid about the error message.
just assert that there was indeed an error. this way, sharding tests
may run 6155_drop_pk.js and still pass, even though the error message is
slightly different in a sharded environment.
- Do not error out on duplicate-case dbnames with sharding and fix the
dbcase test.
- Also fix sharding_passthrough to skip tests that should fail in a
  sharded environment.
Remove obsolete tests
closes #206, fix replset1.js
refs #209 Add a test for the issue and implement the fix. We just need
to swap the start and end keys in prelockRange for reverse cursors.
Do a bit of refactoring around 'direction > 0' since it shows up a lot
and is better described as 'forward'.
Revert "refs #209 Add a test for the issue and implement the fix. We just need"

This reverts commit b9dec354b8f9878d4813d76982e66dc474a78d5c.
closes #208, don't access BSONObj belonging to cursor after done working with cursor
closes #207, fix replset5.js
support big transaction on the primary
#93 rebase
#93 copy remove oplog.refs to local oplog.refs
#93 get or create an oid when spilling
#93 use a DBDirectClient cursor for reading the local oplog.refs
#93 add some bigtxn tests.  some crash.
#93 rebase