Add a "forced" script update context menu item.

This feature _always_ overwrites the local script with the remote version.

Fixes #1743
Only use Coral CDN when it works.

In some cases, Coral is blocked and will not function properly.

Refs #1722
Custom meta-data block format. Fixes #1753
Custom meta-data block format. Fixes #1753
Simplify and rename the new user script template.

Refs #1752 Refs #1753
Do not advertise an un-implemented interface.

Fixes #1763