[TIP] unittest2, distribute, and doctests

[Robert Collins]

Related to regexp filters, I really want two things in core; I have
implementations in various places I can propose when trunk unfreezes.

Firstly, getting the filter (whatever it is) from a file, with one
entry to the filter per line, entries are OR'd together.

Secondly, an exact match filter - where the filter specifies the test
*id* (and applies *after* load_tests, because that permits both
parameterisation that multiplies tests and changes ids, and doctests
where the ids are not directly importable python names).

-Rob