Batch synonyms from a csv file

[willm]

Allow importing synonym rules from a CSV file, this saves users from having to go through the form multiple times to enter many synonyms. This implementation is very basic, it only supports synonym rules and doesn't add any tags. This can be extended if this is deemed useful.

I've used the papaparse package to parse the csv data.

Note I built this from the latest release commit rather than master because I'm having trouble to build/run the master branch, I think some versions of java/node have changed which I'm struggling to get right.