[#198][#205] Minor syntax fixes, Improved Makefile

Created by: elbenfreund

This PR is a direct copy of Raphaël Hertzog work (#217 ) with just minor (mostly markdown related) changes to commit messages.

This PR does tree things:

• Avoid creation of duplicated convinience.js files
• Use var instead of const to export variables
• Fix broken argument list for Gio.bus_watch_name()

In effect this seems to fix several outstanding bugs. For the original PR message and further information please refer to #217

Fixes #205 (closed) #198 (closed)