Support fetching UIDs from index at root

algo/uidlist.go

cmd/dgraph/main.go

cmd/dgraph/schema_scalar

geo/filter.go

geo/filter_test.go

gql/parser.go

gql/parser_test.go

gql/state.go

gql/state_test.go

lex/lexer.go

query/generator.go

query/geo.go

query/geo_test.go.disable

query/query.go

query/query_test.go