The rbintegrations extension is a core part of the Review Board 3.0

feature set, and we want to reduce the number of hoops required to start

using integrations. This change marks the extension as being

auto-enabled by default when first registered by the extension manager,

meaning that 3.0 users will automatically have it enabled. Beta users

will have to enable it manually.

Removed the registration for rbintegrations and re-scanned for extensions.

It found rbintegrations and auto-enabled it.