SCUBA2: delete _GET_FTS_CONFIG_ primitive

This was used by the old _FTS2_DR_ primitive which was removed in
commit f31eda7430.  The primitive is not used and refers to
files which do not exist.
SCUBA2: re-read header in _MASK_FTS_MAP_

This resets the headers and is necessary here because
this primitive alters the number of files in the frame.
SCUBA2: update REDUCE_FTS_POINTING recipe

This now makes use of the _MASK_FTS_MAP_ primitive and then
applies the standard pointing steps.  Also added an
orac_say to _MASK_FTS_MAP_ to indicate what is going on
at this stage.