Zabbix

A......... [DEV-3914] restricted access to media type fields for users of User and Admin types; added strict validation for "filter", "search", "output" parameters of mediatype.get API method

* commit 'b4ee5582f7e7459c90ca530f1136f5343a30a2d3':
  ..F....... [DEV-3914] fixed inability to specify media types for Action log widget
  A......... [DEV-3914] fixed undefined index error appearance when user of type Admin sent a valid request to mediatype.get API method
  A......... [DEV-3914] minor improvements
  A......... [DEV-3914] fixed coding style according to guidelines
  A......... [DEV-3914] fixed incorrect condition
  A......... [DEV-3914] minor improvements
  A.F....... [DEV-3914] replaced string constants DB::FIELD_TYPE_* with numeric ones
  A.F....... [DEV-3914] implemented a new constant DB::SUPPORTED_FILTER_TYPES; both constants are now used throughout the code related to filters
  A......... [DEV-3914] simplified code
  A......... [DEV-3914] fixed undefined index error in mediatype.get API method
  A......... [DEV-3914] removed mediatypeid parameter from responses of mediatype.get and alert.get (when selectMediatypes is requested) API methods for a case when it isn't requested
  A......... [DEV-3914] restricted access to media type fields for users of User and Admin types