Precision of RA and Dec output

[MatthewWhiting]

It was pointed out by the reviewer of the MN paper that the RA and Dec columns in the output file have the same precision. Normally you would expect RA to have one place fewer than Dec, as it is in different units.

The 2 decimal places are actually hard-coded in the decToDMS function. This should be changed to make this precision an input parameter.

Further than this, the precision used here should reflect the input data - if we have, for instance, degree-sized pixels, you don't need this level of precision. But if we have micro-arcsec pixels you need hugely more...