issue #1360

It is possible to have multple  given contexts in a single BDD scenario;
if you have to type 'and' in the GIVEN description; it's very likely you
need an AND.

A generic AND  is not possible, thus a AND_GIVEN  is added to complement
the AND_WHEN and AND_THEN.

Can be used without needing to increase indent:

	SCENARIO("...") {
		GIVEN("...")
		AND_GIVEN("...") {
			WHEN("...") {
				THEN("...") {
					// ...
				}
			}
		}
	}

would correctly output, when requested/needed:

    Given: ...
And given: ...
     When: ...
     Then: ...

The padding had to be increased by a character in the output message, to
continue to be uniform.

The support is to be considered experimental, that is, the interfaces,
the first party generators and helper functions can change or be removed
at any point in time.

Related to #850