Allow "X-HTTP-Method-Override" in request.

Client may send a POST request, but override the method to newer methods (e.g. PATCH, PUT).
Merge pull request #138 from Gizra/137

Allow "X-HTTP-Method-Override" in request.

Client may send a POST request, but override the method to newer methods (e.g. PATCH, PUT).
Add \RestfulInterface::publicFieldsInfo() for declaring fields.

Use \RestfulInterface::getPublicFields() to get the processed fields (i.e. with default values initiazlied).