Change all plugin option names to use the same prefix

As per @leogermani's [suggestion](https://github.com/leogermani/babble/commit/ccf0c603c32802697441606414f4483e62669e6b#L1R56), we should use the same prefix for all our options. That prefix should be `bbl_` (arbitrary decision, but matches the API function prefixes).

As part of this change, we will need update methods in the affected classes to create the new options with the correctly prefixed name, populate the values appropriately, and then delete the old options.

Start by locating the affected classes and the methods that create or populate plugin options. Trace each option's current name and value handling, then verify that every option uses the bbl_ prefix, values are preserved, and the old options are removed.

Written by the indexing model from the issue text.