Fix the terminology around the WGS84 TCRS

[prushforth]

Specifically, it isn't a wild-card, but a stand-alone TCRS which has a gcrs of WGS 84, as do other TCRS, however, not all share it.

WGS84 serves as a "wild-card" projection

Discussion of TCRS needs review and update.

Originally noticed this in a recent PR, points to need to get going on a new generation of specification.