Execute a meta-analysis with the click of a button.

[jdkent]

Give users the option to execute a meta-analysis with a click of a button.

[nicoalee]

Trigger a new job
POST /meta-analysis-jobs

Get all meta-analysis-jobs for the current user
GET /meta-analysis-jobs

Get a particular job's status and logs
GET /meta-analysis-jobs/{job_id}

[nicoalee]

also addresses #679

[nicoalee]

also addresses #680