Move various TODO into top-level TODO file
regen for ./TODO
TODO: tests for getkey_(double|integer|string)
release lkonf 0.4

* Rename type lkonf_t to lkonf_context.
* Provide lkonf_keys typedef for array of table key names.
* Provide key-based variants to lookup values:
	lkonf_getkey_boolean()
	lkonf_getkey_double()
	lkonf_getkey_integer()
	lkonf_getkey_string()
regen for lkonf 0.4