Change string length back from 1024 to 64 in mask creator

[xylar]

This is necessary for compatibility with MPAS-Model, which hard codes a 64 character string length (!!!)

This has the unfortunate effect of cutting short long feature names stored in strings in files generated by the mask creator.

[xylar]

@mark-petersen, I know it's a busy day today but could you take a quick look at this? I want to merge before making a new release for @matthewhoffman

[xylar]

Testing

I ran the tests I use in the conda package:

MpasMeshConverter.x mesh_tools/mesh_conversion_tools/test/mesh.QU.1920km.151026.nc mesh.nc
MpasMaskCreator.x mesh.nc arctic_mask.nc -f mesh_tools/mesh_conversion_tools/test/Arctic_Ocean.geojson

The result is:

$ ncdump -h arctic_mask.nc
netcdf arctic_mask {
dimensions:
	nCells = 162 ;
	nVertices = 320 ;
	nEdges = 480 ;
	nRegions = 1 ;
	nRegionGroups = 2 ;
	maxRegionsInGroup = 1 ;
	StrLen = 64 ;
...

So the string length is back to 64. With the current release (0.0.4) it's 1024.

[mark-petersen]

Yes, I can see why this is needed. @xylar thanks for being attentive to these issues. Please merge.