Restore JS naming convention

The customizer control was not hooked up to the JS behavior
because the PHP identifier did not match the JS identifier.
Fix customizer control and un-namespace readme generator class
Update settings instead of controls

Corrected method for updating customizer, by updating settings not
by updating controls. This is the right way to do it, but it also
now causes updating serialized/array settings to work properly, for
example those used by the Styles plugin.

/cc @pdclark