Distinguish between vanilla FAIR features and the ext-wp extension

[johnbillion]

FAIR started as -- and is currently focused on being -- a tool for the WordPress ecosystem, but WordPress-specific support is actually implemented via the ext-wp extension to the FAIR protocol. FAIR itself is ecosystem-agnostic.

fair-tools needs to make this distinction clear. Step one is probably to add wp- specific naming to commands that deal with WordPress plugins or themes and wp-ext extension metadata.