add test for "raw" body encoder
add sanity https support and refactoring AdvancedAgent
fix AdvancedAgent inheritance test
fix AdvancedAgent.pool usage test
fix "agent persistence" test
fix "global and default pools sizes is 1024" test
fix default AdvancedAgent behaviour

* remove `protocol` option for Request.getAgent
* default `protocol` option for Request as of http.request
  ('http:' or 'https:')
* most of tests are done
fix "non-persistent agent" test
fix test of "Request.getAgent for non-existing agent name"
fix test of "Request.getAgent for existing agent"
fix default port for https, rename agent to agentFactory, fix tests
fix tests