handle paths with whitespace in Windows launchers

[djdv]

When installed in a path containing whitespace, invoking the server from my editor returns this:

'C:\Users\Firstname' is not recognized as an internal or external command,
operable program or batch file.

My user directory is like: C:\Users\Firstname Lastname.
Quoting the path (from %~dp0) resolves this and shouldn't cause problems with paths that already worked.