Move admin controls from anon functions to public ones

Using  to reference object variables isn't available in PHP
anonymous functions before 5.4.x, so this was crashing in the client
environment of 5.3.x
Made less clean, but fixed, by moving to separate callback methods
like WordPress kind of expects anyway.
Update setting namespacing to be backwards compatible

Wordpress on old PHP was failing to save settings named with the
actual namespace, so translate backslashes to underscores for
setting name strings.