R1:b62ecb7c1159

Make UX for misspelled or delted config much less bad

Summary:
Fixes T3436. Currently, when installs have configuration options which we don't know about, we raise a fairly confusing/ambiguous message about the options being unknown. Instead:

- Keep a list of previously valid (but now deleted) config, with explanatory reasons for what happened to it. Present this information, along with altenate wording ("Obsolete Config" instead of "Unknown Config") where applicable.
- Show a list of all the places…