refactored xfeatures2d in the same style as features2d
fixed xfeatures2d tests
corrected text detection once again to match the new MSER interface
added properties setter/getter to SURF
fixed some more compile errors and test failures
Merge pull request #113 from vpisarev/refactor_features2d_take4

Refactored features2d & xfeatures2d
ruby bindings: inital commit