Feature/metadata remediation tests

@NYULibraries/hydra I added integration tests for adding, editing and deleting metadata for nyucore records and added to the existing specs as well.

Haven't figured out the scenario `Adding a record with multiple values in all multiple fields` yet but will get there. It's currently labeled `@wip` or Work In Progress so it's getting skipped.

I'd appreciate anyone who could take a look at this and help me improve.