Refactor ScienceBase user setting to support updated "publish-options" schema

[hmaier-fws]

Refactor how ScienceBase user setting are stored in and read from the mdEditor-Json "type": "settings" object. The publish-options setting is being refactored (see: #726 ) and existing functions that read ScienceBase user settings will need to be updated.

tasks:

• Update settings schema as described below
• Update existing ScienceBase functions that read user settings
• remove the rootURI element from lib/mdeditor-sciencebase/addon/utils/config.js file.

Proposed settings schema:

"publish-options": [
  {
    "publisher": "ScienceBase",
    "publishEndpoint": "url to ScienceBase publishing endpoint (string)",
    "sb-defaultParent": "identifier of ScienceBase parent item (string)"
  }
]

[hmaier-fws]

@dvonanderson a general comment regarding PR #765

The objects in the settings publish-options array use the catalog key to identify the various publishing destinations. The potential "publishers" may not be "catalogs". The current catalog key should be changed to another more generic term such as publisher (see #726 (comment)). The remaining options are specific to each publisher so there should be no need to standardize those.

However, all publishers should also have an endpoint, but I'm not sure it's necessary to standardize that term across all publishers, unless you see some benefit to doing so.