assertEq and assertNe utils replaced by gotest.tools/assert, deleted these utils.
Implemented proper serialization of JSON patches: all simple types in values are converted to sting, all maps of interfaces are converted to maps of strings. I.e. implemented applying of JSON patches directly from values in policies.
Implemented checking of incoming request to correspond the policy rule, added tests.
Implemented generation of JSON patches according to patches in policy object, added tests.
Implemented base version of Mutate function as a wrapper for all mutation functions.