Create tab in myDIG GUI to show list of custom extractors

[szeke]

The tab should list all the custom extractors with the following columns:

• name: as defined by the method to get the name of the extractor, from code or annotations, however this is implemented.
• PyPy url
• version that the user want to use. This displays the version of the extractor that is currently installed
• action:
  • delete: deletes a custom extracor
  • update: pulls in the latest version of the extractor

In the initial version, the user cannot specify the version. The system will always get the latest version when the user updates.

A pop-up should inform the user that the extractor will start working after the user restarts the extraction pipeline.