Add enable/disable checkbox for each node body insertion element, and use that setting during insertion.

Issue Summary

It would be very helpful to be able to enable/disable each insertion element rather than remove the insertion template text in order to disable that element.

For example, if you want to temporarily disable the "Inline insertion" behavior, you have to delete the inline insertion template. When you want to restore the insertion, you have to re-enter the inline insertion template. Not good.

So, I propose that we add a checkbox to enable/disable each element (Top, Inline, and Bottom).