xml2kvp: validate configuration JSON

[ghukill]

Validate before:

• FieldMapper model is saved
• JSON is submitted for Job running, re-index, or testing

Could be static method on XML2kvp that validates against default types. Or, an actual JSON schema?

[ghukill]

Schema is validated live in jsoneditor, but think it would still allow submission (no JS checks to prevent).

Would still make sense to validate before sitautions above.

[ghukill]

Validation before update/create in fm config form. Keeping issue open if deemed useful to validate before Jobs are run (not just FM mapper CRUD).

[ghukill]

Closing - may revisit later when ES queries get more attention, but there is some schema validation information for users, and again during CRUD operations.