Refactor type system

cmd/dgraph/main.go

geo/filter.go

geo/filter_test.go

geo/s2index.go

geo/s2index_test.go

posting/index.go

posting/index_test.go

posting/list.go

posting/types/types.pb.go

posting/types/types.proto

query/geo_test.go

query/graph/graphresponse.pb.go

query/proto.go

query/query.go

query/query_test.go

rdf/parse.go

rdf/parse_test.go

schema/parse.go

types/conversion.go

types/conversion_test.go