Fix: template reloading

Since pyramid_debugtoolbar is a stand-alone application from the view point of Pyramid, it does not inherit any of the settings from the application it was started from. This means that things like `pyramid.reload_templates` and `pyramid.debug_notfound` are not brought over from the end-users application.

In most cases this is desirable, it becomes problematic when the user is attempting to create a debugtoolbar panel and is constantly modifying the templates.  

This changes introduces a bunch of new configuration variables that may be set, they are outside the scope of the standard Pyramid configuration and are namespaced to the debugtoolbar. This allows one for instance to turn on the `reload_templates` feature in the debugtoolbar, while keeping it turned off in the end-users application.

This would fix this issue: https://github.com/Pylons/pyramid_mako/issues/24 and https://github.com/Pylons/pyramid/issues/1265