OSNG-87 - added enums to the entities with the corresponding canonical values for the type, fixed tests
OSNG-87 - added exceptions if user name and display name is empty, fixed tests due to the json validation changes
OSNG-87 - added validation for the json object (user, resource) to throw exceptions if the structure is incorrect, if the type of a value is incorrect, if the attribute is not known and if the canonical types are violated, generalized POST, PUT, PATCH methods to obtain the user and group resource from the HttpServletRequest
OSNG-87 - added validator class and test to check the json violations
OSNG-87 - fixed group create test due to displayName isEmpty check
Merge remote-tracking branch 'origin/master'