Change Dockerfile to install lua, luajit and love and also to install
nodejs 12 needed to build the lua debug adapter. Create the
love-headless test in support/test/lua to test love without an x server.
Very very basic inital checkin to show a way to talk to/from a Vim job
using python (mainly), and to parse the sort of messages that LSP and
VSCode debugger protocol speak (i.e. similar to http messages).
Very hacky, sort of holds together for what it is.
