dillon1000/react

[be] Access all features flags through Environment

Most of our feature flags are accessed via the `Environment`, but a few cases 
have slipped in where we look at the `config` object directly. The problem is 
that the config object doesn't set defaults, so the check is effectively 
encoding what the default is. 

This PR moves to always accessing flags off of the environment, and adds a few 
flags that weren't yet defined there.