Added LSIF capability to ULSP

[nshapiro4]

Adds lsif.icn into the uni/ulsp directory. This works as a command option in the ulsp command. Can be used to generate LSIF information from a specific directory, or all directories targeted by ulsp.

[Jafaral]

You have a merge commit, you can please rebase on top of master?

[jschnet]

The output.lsif file probably shouldn't be part of the source, unless told otherwise. This can be removed by adding a line to the .gitignore file instead, right after that ulsp line.

Also would be good to remove this file while cleaning using the Makefile, i.e. make clean.

If we anticipate there being more than just this one output file in the future, having a directory called outputs/ in here would make things easier since there would be less to add for instances like this since we can just add that directory to the .gitignore and Makefile rather than each individual file.