Update TEI Oxygen package

[Conal-Tuohy]

• [x] Provide a UI for configuring updates.
• [x] Auto-update option (default yes)
• [x] Check for new version when JEdit starts
• [x] Prompt the user whether they want to update, when an update is found.

[MarjorieBurghart]

When the update is processing, for ergonomy, it would be nice to have a progress bar or some sort of message to the user explaining what is going on?