0.2 moved various modules from Net::IMP and App::HTTP_Proxy_IMP to Net::IMP::HTTP, bugfixes

- move Net::IMP::HTTP_AddXFooHeader to Net::IMP::HTTP::Example::AddXFooHeader
- move App::HTTP_Proxy_IMP::LogFormData to Net::IMP::HTTP::LogFormData
- add tests for both
- make Net::IMP::HTTP::Connection support not only http and stream, but also
  httprq interface
- various fixes to Net::IMP::HTTP::Connection