Allow multiple geometries for each dataset

[avdata99]

Current status:

• The package_extent table has 2 fields: package_id and the_geom but package_id is a primary key. We cannot add more than one geometry per each package :(
• The save_package_extent function check for existing geometries and override them if exists for a package.
• We are using the spatial package extra to save the geojson version of the geometries. We check_spatial_extra after a package is created or updated.