Agree on new JS namespacing proposal

At present, we put all of our JavaScript into a number of namespaces, which are not well codified. These include:

M.<frankenstyle_subsystem>

M.<frankenstyle_subsystem>.<sub_subsystem>

M.something_random

Y.Moodle.<frankenstyle_subsystem>

(and various other variants)

To benefit fully from YUI module sandboxing, we should register all of our Modules in the Y namespace, and we should take the opportunity to agree on a codified specification for this.

I've created a proposal at http://docs.moodle.org/dev/YUI/Namespacing to begin discussion.

This is essentially:

   Y.M.<plugin_or_system_type>[_<component>].<YUI_modulename>[.<YUI_submodule>]

I went for Y.M, rather than Y.Moodle to keep the length low.