Fabric add remote update

This adds nodejs / npm and react tools installation so we can recompile the jsx on the server.
Introducing `install_nodejs` and `install_react_tools` functions, both of which added to the `setup_system` task.

Renamed the `jsx` function and its (only) existing reference to `compile_jsx`. This function now takes an `instance` parameter which, if supplied, will compile the maproulette jsx file on the server. This parameter defaults to None, emulating the previous behaviour which was local compilation.

One thing to consider is to add a switch in the script to either use a local jsx executable in conjunction with a `put` to drop the result on the server, or compile remotely, depending on your environments and preferred workflow.