Verify mappings status in WireMock test container on startup and fail by default when there're no mappings

[oleg-nenashev]

This is an alternative to #69 for #28 that uses the Wait Strategy to verify the response and say the container is not ready if there are no mappings. Unfortunately it is not going help with #28, bacause there is no way to abort the wait loop from the predicate.

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[bitxon]

I like the idea to have validation of empty mapping, but i would allow empty mapping by default and failed container only if developer explicitly asked about that (executed withFailureOnEmptyMappings())