Z Constraint on geometry_columns
Replace Has_Srid by ST_CoordDim
Use geometry header for st_coorddim
remove underscore on ColumnSRID class
javadoc
Merge pull request #114 from nicolas-f/fix/srid_extraction

Z constraint shown on GEOMETRY_COLUMNS view
System functions start with underscore like "_GeometryTypeFromConstraint"

@gpetit @mlecoeuvre `ST_HasZ` has been replaced by `ST_CoordDim`.