Added all migration files needed to mirror the Greece dataset on rs1

This provides four SQL scripts to mirror the schema of the Greece coastline dataset that's already available on rs1. The Greece coastline data is not aggregated on water tiles near the coast (~5-7 tiles reaching into the water) and also is different from the schema we're setting up for the obm_tiles database and table (i.e. cell_id as PK, UTM zone still available). Since for now we are interested in L18 tiles and the completeness values only, this dataset has all we need to populate the Greece L18 database.

. /approve @fd @nicgar /fyi