Support for renaming/moving files

[Ruin0x11]

There is currently nothing in the LSP specification for renaming/moving files, from looking at these issues: microsoft/language-server-protocol#272 microsoft/TypeScript#6487. It is apparently planned for version 4.0 of the spec, with the proposal here: microsoft/vscode-languageserver-node#295. Preferably this operation would not have to initiate a reindex of the project, since the way this would interfere with the current workspace implementation would be tricky to work out.