Calling remove with no arguments resulted in an error b/c
of the lack of options.

Fixes NODE-1287

#1651)

Fixes NODE-1262

If one of these tests fails, it frequently causes false negatives
for following tests. This change properly cleans up after ourselves.

* test(connection string): update to latest tests from specs

* fix(url-parser): catch errors thrown by url parser

* fix(jsdoc): mark db.collection callback as optional

* fix(jsdoc): typo

The fixes are very few in quantity and only very minor issues can likely be ignored. 
> Missing comma after "However"
>Hyphen missing

When the topology believes it has session support, options passed to
commands were getting mutated with the session added to them. It is our
expectation that the driver will never be mutating arguments passed to
it via the public facing API.

This commit creates a new object and copies into it, then replaces in
the args array.

`MongoClient.prototype.startSession` doesn't take a second argument, or return a Promise. It returns the ClientSession from the mongodb-core.

Moves the tracking of active sessions to the topology base.
Doing this allows us to ensure that all active and pooled
sessions are ended when the topology closes, and that implicit
sessions are tracked. Also adds a test case to make sure none of
our unit tests are leaking sessions, and corrects many leaky tests.
Also bumps version of mongodb-core

Part of HELP-5384