Beginning a system for merging subscriptions in the session.

So far just one v. small test, and enough of a shim to get it to pass.
Finished reimplementation of merge box. Needs more tests
Lots of tests for the merge box
Avoid unnecessary equality comparison in clearField.

Minor test changes.
Fix use of incorrect variable name.
Change added api to have id separately
First stage of ddp-pre1 plumbing: livedata-server.js
Fix bug in _SessionDocumentView where objects are not maps.

Generally clean up use of 'in'.
mongo_driver.js modified to use added-changed-removed. Tests do not pass yet
DDP-pre1 sends "method updated" messages as msg=updated, not msg=data.
Client-side changes so ddp-pre1 affects minimongo
Some self=this adjustments and now basic apps work
tinytest support for ddp-pre1
Attempting to get set userid working
Most of livedata_connection_tests adjusted
Fix order of arguments.
More fixes for DDP rewrite. 'livedata' tests pass.
Clear fields properly.
Should not be in loop.
Fix concurrency issue with yielding runHandler.

All tests now pass.