Jsonize furniture and terrain, part 1

This PR moves both terrain and furniture declarations from two huge blocks of static initializers to two JSON files, using the shiny, new and improved JSON loading format. I couldn't JSONize one without doing the other, as they both used the same t_flag enum (which has been replaced with string flags).

The ter_id and furn_id enums are still present and are still used to index into the vectors-that-replace-arrays of terrain/furniture types, so this ~~will~~ should **not** break save compatibility. It also means you still have to add constants to those enums to add new terrain/furniture types. Removing those will have to wait for another PR.

I made heavy use of find-and-replace to format the JSON properly, probably resulting in the first time in history that the following scenario has occurred: I had a problem, so I used regular expressions, and now I have no problems. Still I would appreciate a few eyeballs checking that I didn't misspell any of the string flags while I was replacing those; I checked myself, but I might have missed some.