HM/TS: First stab an incremental response-data processing using a callback for httpget(...).
TS: testHttpGetStreaming implemented with referenceHttpServer's StreamingData

WeightlessTestCase's referenceHttpServer now has an optional
streamingData argument.  Add in a StreamingData-object which is either
initialized with data or fed data using doNext's optional data argument.

In the test call .doNext() to let the reference HTTP-Server send
another piece of data on its socket.
TS: comment typo fixed
TS: tested and fixed httpget (_do(...)) with really large headers.

Improved _httpreader's _do(...), better reactor cleanup after
exceptions - less reactor-logged exception-noise.
TS: enabled tearDown assert for dangling Reactor processes.
JPM/TS: new Seecr-Test in lib for testing.
JPM/TS: SSL Handshake extracted, handshake exceptions are now thrown into suspend.

Refactored while ... into _loopReactorUntilDone() in AsyncReaderTest.
TS/JPM: processPartialResponse now also supported in httpsget, httppost and httpspost.
JPM: added prio kwarg + 'keep alive' socket options to httpget and httppost