Reimplement PLAY_ as a separated class

Introduces a Player class to handle the special delay functionality, and
move all of that junk out of the main init module.
Move on-the-fly initialization into function

Takes the reviewer and its associated filter and wraps it in a function
to be called from the loader.
Wrap the configuration menu insertion in function

This one does not have any local variables to seal off, but makes it
easy to disable.
Wrap update check in function, reorganize

This puts this functionality into a function that can be dummied out now
and reorganizes the others.
awesometts.editor_button()

This one controls the editor button on the Add and browser windows, as
well as automatically disabling/enabling it.
Shortcuts and move some imports

Wrap the shortcut configuration setup and move some imports into
closures.
Browser menu component

Makes this loadable like the others.
Card layout button

This is now wrapped in a function, completing the set.
Tighten up init module

Collapses some non-critical nested areas.
Mention restarting Anki when editing loader

This might be missed if not mentioned, as no changes take effect until
restarting.
Fix for mass generator crash on Windows

If the user cancels the mass generation while a throttle timer is
running, this causes a crash on Windows, as the timer is not stopped
when it is garbage collected.
Merge branch 'chg/init-cleanup' into develop

Brings in some needed clean-up of the main module and the ability for
end users to turn off a subcomponent that is causing problems.