Data Explorer is slow

Currently, the Data Explorer tab will count predicates in batches of 4, every 2 seconds. This causes a significant delay for graphs with many predicates, since a large portion of time can be spent waiting for the 2 second timer to expire.

https://github.com/dgraph-io/ratel/blob/43115275eeff79b593dafada22916dc17fe92045/client/src/components/DataExplorer/index.js#L116-L128