Possibility to check if one of orthogonal states is as expected

[pborzecki]

The idea is to have possibility to test orthogonal states independently. I.E. for testing purposes.

[rhard]

@pborzecki @krzysztof-jusiak If the utility could not be a part of the distribution, could you help me how to convert it to the standalone function. Just tried different approaches, but without success. Unfortunately, I'm not fit in the metaprogramming. A little example would be very useful.

[guiserle]

Actually, this should be the behavior of is<TState> according to user guide. More info can be seen on #481