RSM

..F....... [DEV-1408] removed legacy mixins and css prefixes

* commit '38b0d834c37cafcc871b6aaf658e75c514882a26':
  .......... [DEV-1408] removed non used file
  ..F....... [DEV-1408] fixed placeholder color for IE and Edge
  ..F....... [DEV-1408] fixed and optimized scss code style
  ..F....... [DEV-1408] removed unused comments and fixed code style
  ..F....... [DEV-1408] updated legacy scss includes and css prefixes