* DEV: `Discourse.baseUri` does not exist
This never could have worked - should have been `Discourse.BaseUri` if
anything.
* DEV: Remove Discourse.Environment
* DEV: Remove `Discourse.disableMissingIconWarning`
* DEV: A bunch more missing environment checks
This is to help with the migration to Ember CLI. In the current running
version of Discourse everything should be the same as before, just with
a few extra files that are not used. However, using Ember CLI this can
be installed as an Ember addon.
Co-Authored-By: Jarek Radosz <jradosz@gmail.com>