Saved field mapping configurations for Jobs

[ghukill]

Now that xml2kvp is settling into place, which allows for on-the-fly adjustment of field mapping configuration JSON, it might be beneficial to store this JSON with the Job.

While there is now a FieldMapper model, which can be used to save configurations that will be reused, users may also edit this configuration JSON on the fly before a Job is run or re-indexed. This has proven to be quite helpful, but there is an air of mystery about how field were mapped unless this configuration is saved.

Proposing adding a new column to Jobs, something along the lines of fm_config_json, which matches variables elsewhere.

[ghukill]

Adding Field mapper configurations (fm_config_json):

• when Job's init through CombineJob
• before a re-index

Adding this to pre-existing job_details column

[ghukill]

Done.