Re-add "Enable Damage" to Finetest's builtin (or turn on if "Creative Mode" is unchecked)

[Jacob Gustafson]

Problem: There is no "Enable Damage" checkbox. Finetest has no way to enable (make environment affect) damage, hunger, or breath meters.

• The conf setting that affects these is enable_damage.

Alternative solution:

• #633 (Apply the proposed Classic change to Finetest: use single Creative Mode checkbox, and uncheck it to enable damage)