Performance improvements and bug fixes

Handle language when forming NQuad. Move the fp mod earlier in the process, to avoid paying for ToEdge() function call.

Aync writes to RocksDB are 1000x faster than sync writes. We don't need to do synchronous writes because we do sync writes on commit logs

Fix a bug due to which we were unable to retrieve xids.

Batch write while merging

Tool to debug posting lists in RocksDB

RocksDB merge in go

Change log output

Testing Distributed Loader

Set the number of goroutines for gentle merging to 18. It is little slower to run these goroutines, but they keep the memory usage in check.

Store any errors encountered while running the pipeline. If any error is found, stop processing immediately. Switch the system to sync.WaitGroup completely, instead of an error channel. Log fatal on error in loader and uidassigner

Loader shouldn't cause uid assignment. Add a Get() function in uid, and avoid calling rdf.GetUid. Plus, other changes across the entire code base to accommodate this.

Change how many keys we merge. Also, run gentlyMerge in a goroutine, so our memory monitor can call aggressivelyEvict in time. Also, with this change, the memory growth is a heck of a lot more controlled.