smurf: Ensure JSA tiles have a defined telescope position in the WCS

The ObsLat, ObsLon and ObsAlt attributes are now set to the position of
JCMT as defined by PAL. I initially copied the position from an input
smfHead, rather than just using the PAL position, until I realised that
the position needs be defined consistently whether or not a smfHead is
available. For instance, no raw data is available when determining a list
of tiles that touch an arbitrary sky region.
smurf: Ensure ObsLat/ObsLon are equal in SkyFrame and SpecFrame

The values stored by makemap in the output SkyFrame are copied to the
specframe. But the SkyFrame values returned by AST are rounded to the
nearest 0.01 arc-second, so the values stored in the SpecFrame end up as
rounded versions of those stored in the SkyFrame. This changes rounds
each value to 0.01 arc-sec (about 30cm on the earth's surface) before
storing them in the skyframe, so both frames end up with the same value.