Support CSV parallel encoding

• Add a toggle in the UI to enable.
• Add check if file is large enough to encode in parallel.
• Each record will be passed into a channel where they will be consumed by a couple of goroutines.
• Typically encode 3 times faster than normal for large files.

*Maybe we could do a generic goroutine and apply it to all the other file types and databases. This only involves changing the channel type.