add FieldNameCasing=* to DataSourceConfig

[nvkelso]

FieldNameCasing={upper,lower,exact}.
Default: exact.

Suggested location: DataSourcesConfig as an option there.

1. That way I could point my datasources at a new config file, and it would automatically have this UNIVERSAL FOR ALL LAYERS IN THE CONFIG flag set.
2. Per layer setting in DataSourcesConfig for this would also be super awesome. See OpenOffice example below.

If I pointed it at a PostGIS based list of layers, I could set it to lower and it would automatically turn all my fieldnames in the MSS file to lowercase in the Mapnik XML output.

Note: filters based on fieldnames, text-names based on fieldnames, etc with eye towards Mapnik 2.1 where more properties are data driven.

If I point it a regular SHP file, I would usually leave this property out, since it defaults to exact matching what the fieldnames are already.

But sometimes I edit a file in OpenOffice and that software has a nasty habit of UPPERCASING all my fieldnames. In those cases, if I'd edited all my files that way, I'd set this to be upper. If only some, then I could set that LAYER as upper.

Use case 1 is more important to me than use case 2.

Tnx!