Refactor Convert to accept TypeID as second parameter

cmd/dgraph/main.go

posting/index.go

query/query.go

query/query_test.go

rdf/parse.go

types/conversion.go

types/conversion_test.go

types/date_test.go

types/geo_test.go

types/geofilter.go

types/geofilter_test.go

types/s2index_test.go

types/sort_test.go

worker/backup.go

worker/sort.go

worker/task.go