Remove read_stx_conf() and get_stx_coordnum() uses

Remove read_stx_conf() and get_stx_coordnum() uses

Replace all uses with read_tps_conf(), which is superior in multiple
ways:
 - It removes the need for most boilerplate code needed to read stuff,
   and makes the ugliness of needing to read the same file twice
   internal to confio.cpp.
 - read_tps_conf() at least provides an API that makes it possible to
   not leak memory.  Nearly all callers that used to call
   read_stx_conf() still leak it, though, including read_tps_conf(), but
   at least it is now possible to fix incrementally.

Change-Id: Ic489087f5947bbfd764a1801cbf4e85cb046a812