Debate moving urls of co-ords plugins into real config

[james-rae]

The urls to lookup co-ordinate info are hardcoded in the plugin (see top of index.ts). Which means if we need to adjust them, it requires a re-build of RAMP.

Ideally they would reside in the viewer config under plugins.coordInfo (or whatever the proper name is for the plugin).

However, this does add an extra step in using the plugin (add the plugin, plus add the config element). It won't work without it. Side thought: do plugins need an optional "how to setup" doc feature for people?