Extend meta-portal term search to cover additional sources

[cmungall]

Terminology note: 'meta-portal search' is the term we used in the grant to describe the ability to do search, autocomplete etc over different term sources.

So far we have a nice generic framework with the ability to plugin existing APIs, have demonstrated this with OLS. Need to also extend to e.g. BP

[cmungall]

Be good to have this be a bit more plugin like: https://github.com/INCATools/table-editor/blob/47138af815ff6bcebad8bce72c8e199d92998e91/app/services/session/session.service.js

[cmungall]

It may be necessary to do this for NCIT for one of the patterns in ECTO (activity.yaml)

[DoctorBud]

@cmungall Agreed about making the xxxLookup() functions pluginable.