Makefile-js: Remove reduntant dependencies

config.js and path.js are included in $(js_files).

https://bugzilla.gnome.org/show_bug.cgi?id=731031
Makefile-js: Don't include generated files in dist

Make sure we filter out the built sources from the js files
list before adding it to EXTRA_DIST.

https://bugzilla.gnome.org/show_bug.cgi?id=731031