Manage null values in ST_ACCUM
Improve st_transform to support all single multi-geometries
Make some small corrections
Merge pull request #333 from nicolas-f/fix/st_accum

Manage null values in ST_ACCUM
Merge pull request #338 from ebocher/st_transformFilter

Improve st_transform to support all single multi-geometries
Now we use a geometry filter operation. Please read #307