Investigate blocking evercookie-like tracking

[cowlicks]

The extent of our supercookie detection is currently limited to localStorage based tracking. However there are many other vectors through which an origin can set a uniquely identifiable token. evercookie is a tool that tries to use as many of these as possible to redundantly store some unique token.

We may be able to detect sites using evercookie using a method similiar to our new fingerprint detection heuristic (#1505). We can monitor the API's which are vectors for supercookie tracking, then when an origin accesses some unusually high number of these API's, we can mark it as tracking.

[ghostwords]

Previously: #616.