Settings parsing should be stricter

Motivation

See !1023 (closed) for a bug fix that was harder to find than it should of been.

Proposal

RTS ways and other richer fields (booleans I believe are already strict with YES/NO/failure) should be parsed more strictly, so "YES" is not a valid RTS ways list.

Perhaps we might replace that file with something standard like JSON, too, so richer stuff isn't another ad-hoc language within the string literal.

CC @int-index