Deprecate the use of PluginFetchResourceListFromDrupal

[mjordan]

PluginFetchResourceListFromDrupalView should be used instead of PluginFetchResourceListFromDrupal since it offers as much flexibility in determining what resources to check as site admins can build into a View.

Steps to take in deprecating PluginFetchResourceListFromDrupal:

• Note in the README that this plugin is being deprecated.
• Add a note to the plugin source file and sample_islandora_jsonapi_config.yml that the plugin is being deprecated.
• At the defined date (end of 2020) remove the plugin's class file and the sample config from the Riprap codebase.
• Remove descriptions from the README of using this plugin.

[mjordan]

The "Generate Riprap configuration settings" option in Islandora Riprap's settings form assumes use of this plugin. When it is removed, that code needs to be updated.