Initial implementation of a metaprogramming function, that is capable of detecting element index in variant::types. Some tests to make sure that no old valid code was broken
Started the work on polymorphic_get to determinate sanity/safety of getting Base type. Fixed an issue with polymorphic_get<const final>. More tests, added safe_get and unsafe_get methods. Minor update of the docs
Make polymorphic_get U type  compile time checked, add more tests and improve docs. Use strict as a default policy for polymorphic_get and get (as recomended at mailing list discussions)
Apply naming recomendations from mailing list discussion: unsafe=>relaxed, safe=>strict