Add helper modifiers support

[ameshkov]

• first-party -- This is the very same as ~third-party

• xhr -- this is the very same as xmlhttprequest

• popunder -- the same as popup (needs investigation)

• 1p

• 3p

• all

• css

• frame

[hmage]

Already done.

filtering/urlfilter/src/urlfilter.cc:956

[ameshkov]

Hmm, what about tests? Do we need it to add tests to the android library code?

[hmage]

Yeah, having tests is nice idea, right now there's no test that covers this -- it should be relatively simple to add -- just see if first-party is accepted and if rule matches the way it should.

[ameshkov]

Re-assigned to myself then

[sxgunchenko]

core/pull-requests/1437