Toggle source/target srs when loading CSV

If GIS: source + target, else no source nor target
Use comma-separated-values to parse csv header
Pause stream when first chunk has been read
gdal 1.10.1 virtual driver requires geometryType

... to be set as wkbUnknown, the default value,
or else geom data is not loaded
Cast column names to string
Merge pull request #12 from kapouer/master

more csv driver changes