HG Tier 2b Economy (External Economy)

[CampbellCrowley]

This is planned to be a premium feature This is an extension of #103 and will probably be included with the same unlock requirements.

Adds support for economy systems managed by external sources. Currently I plan to support UnbelievaBoat's economy (#93) with the initial release, and potentially expanding to other bots and services as requested, and possible.

This is planned to follow the same requirements to unlock as #103 . (Subject to change)