GPII-784: Framework is now supporting the new NP set format

GPII-784: Updated all the NP sets, tests, etc. to use the the NP format. The MM has been hardcoded to pass on the "gpii-default" context to the rest of the framework until we implement the context manager, etc.
GPII-939: Updated the grunt script to json lint the testData folder as well
Currently this function is used when merging the metadata sections of preferences sets. The current implementation will return undefined if both arrays are 'undefined'. I think this could be considered appropriate behavior, since if we're merging two preferences sets, both of which have no metadata sections, the resulting NP set should not have a metadata section either..

Does this sound acceptable to you, or should the resulting NP set rather have an array. If we stick with the current functionality, I'll ofc update the description of the return payload to say that if both inputs are undefined, undefined will be returned