Signed-off-by: Aurélien Labrosse <aurelien@pollen-metrology.com>

* Implement POST HTTP method in HttpService (query params and file upload)
* Implement GET HTTP query parameters management following Servlet(c) API
* Implement PUT HTTP method
* Implement HttpRequest#GetBody() to allow raw content processing
* Implement management of file upload using POST/multipart, following the Servlet(c) API
* Allow to specialize (and hence override methods off) HttpServletRequest and HttpServletResponse
  to allow easy unit testing of Servlet implementations
* Allow to provide options to CivetWeb when starting a ServletContainer
* Implement unit/functional tests for HttpService
* Allow to run GTest in a HttpService-enabled environment
* Unit-test various HTTP requests

Signed-off-by: Mael Jannsen <mael.jannsen@pollen-metrology.com>
Signed-off-by: Galil Mori <galil.mori@pollen-metrology.com>
Signed-off-by: Lucas Freyssinet <lucas.freyssinet@pollen-metrology.com>
Signed-off-by: Thibault Friedrich <thibault.friedrich@pollen-metrology.com>
Signed-off-by: Aurélien Labrosse <aurelien@pollen-metrology.com>

* Light IContext is added to allow essentially mocking
  of the context. This allow to test modules using services
  without starting a full framework, injecting mock implementations
  in the context.

* HttpService main classes has been reified to interface
  to allow them to be mocked. This allow to test servlets
  implementation without the need of a complete framework
  to be started.