Define ScienceBase metadata publishing endpoint in user settings

[hmaier-fws]

Currently, the mdEditor only supports publishing to the ScienceBase publishing service, with the url to the publishing API embedded within the code. However, users should have the ability to publish to any custom endpoint. An initial step toward providing a generic mdJSON packet to any API, is to allow users to specify the desired end point.

Initial support for a generic publishing feature can be implemented by:

• Adding a "Metadata publishing API URL" field below the "mdTranslator API URL" field on the Settings page.
• Modify the ScienceBase publishing function ("ScienceBase" button on the Publish page) to obtain the publishing API URL from the value entered on the Settings page.
• The value for the "Metadata publishing API URL" should be read from, and written to the saved settings

[hmaier-fws]

This should probably be under the "Publishing Settings", "ScienceBase" panel.

It looks like the publishing settings are stored as an object. Likely because there was a vision to allow for multiple publishing endpoints. We've been discussing possibly having a generic publish feature that passes mdJSON to any api (which would be defined in the settings). Also, since we now have an option to connect to a CouchDB, we could probably add some defaults for that.

Currently, the publishing options are exported in the settings object as:

{
  "id": "<setting ID>"
  "attributes": {
    "compress-on-save": true,
    "show-splash": false,
    "keep-settings": true,
    "auto-save": false,
    "publish-options": "{\"sb-defaultParent\":\"<sb parent ID>\"}",
    etc....
  }
}

We'll probably need to discuss the best way to structure the publish-options object to support multiple publishers.