[#2590] Update http mock to match on method and persistence and allow custom response message.

Problem
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We need to extend the HTTPMockServer and its handler to help with testing or our server.

Changes
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HTTPMockServer was created as a quick and dirty hack to test simple web requests.
At the start I did not believed that it is of much use and that it should be replaced with something better...
it turned that that with a bit of helpers it can be useful ... so here I have extended it and added tests.

This is not really a mock, but a real server, as it listed on TCP and handles real requests.
I have renamed the class names to better reflect what they are... the Mock name is too generic.

The current implementation is based on "Backend Definitions"  as the order in which requests are made is not
enforces.

For Request Expectations vs Backend Definitions see https://docs.angularjs.org/api/ngMock/service/$httpBackend

This changes will break the API, but I will create a new branch on server to integrate the changes.
This changes also check persistence connection by default.


How to test
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reviewers: @alibotean 


check that changes make sense.

Thanks!
Let's use HTTP instead of Http as for the rest of the class nomeclature.