CodeCompliance_Engine: Check Adapter namespaces contain external

Linked to: 1) https://github.com/BHoM/Test_Toolkit/issues/72#issuecomment-596234396

And: 2) https://github.com/BHoM/BHoM_Adapter/issues/210

And: 3) https://github.com/BHoM/Test_Toolkit/issues/72#issuecomment-596416344

There is a new compliance rule that adapter projects namespace should be as described in 2 above.

However, we have previously found that namespace checking can be tricky to cover for all situations when running CI checks. Previously we did it based on the filepath which looked for the toolkit name, but this prevented the ability to inject into existing namespaces without flagging as a CI fail.

We would need a similar set of discrete rules which allow the CI to know if a namespace should include the External keyword or not.

This issue is to discuss that, and see if such a set of clear rules can be found that will allow for the creation of a CI check to aid us in keeping compliance on this new rule.