Figure out elm.json changes without restarting server

[jmbockhorst]

Currently we restart the entire server when elm.json changes. We should explore a system where we can update the necessary parts without restarting the server, which will be much faster. Will need to compare new elm.json vs old one. If dependencies are updated, rerun solver and figure out the diff from the last solve. Add/remove/change packages or versions. If source directories are updated, add/remove source files.