Add enable/disable options to document handlers for a11y and menu

[dpvc]

This PR adds enable/disable document options for the a11y and menu document handlers so that these options can be controlled programmatically more easily. These are the enableExplorer, enableMenu, etc. options in the various MathDocument mixins.

This makes it unnecessary to override the explorer(), enrich() (and similar methods) in the menu code, which simplifies the MenuHandler considerably. The testing that was done in these routines has been moved to the checkLoading() render action. This makes the menu handler cleaner all around; I was never happy about the overriding that was being done there.

I also normalized the handling of the state and process bits in some places, so that the states are set even if the action is skipped (so that attempting the actions that are skipped won't be repeated in the future). This causes some changes in indentation, and makes some of the diffs seem more substantial than they are.

Finally, I added force parameters to force the processing even when the enable options are off (so, for example, the complexity computations can force enrichment even if enrichment is disabled).

[dpvc]

Remember that you can turn off the white-space differences to ignore the indentation changes, which makes it easier to see the "real" changes.

[zorkow]

I like that the code becomes a lot more concise.
However, there is one part I do not fully understand.
While enableMenu allows me to disable the menu as an option settings, enableEnrich and enableExplorer can not be set in options (even with enableMenu true and while I can see the on the document.options).

[zorkow]

We wanted to set this to false in 3.1 and instead have accessibility switched on.

[dpvc]

I want to do that in a separate PR. I always want to do some testing to see what the performance impact is before making that change.

[dpvc]

While enableMenu allows me to disable the menu as an option settings, enableEnrich and enableExplorer can not be set in options

These options are only available when the corresponding component file is loaded. The menu component is included in the main combined components (like tex-chtml) automatically, but the other a11y components are loaded on demand by the menu. So their options are not available unless you explicitly load them yourself. They do not force the loading of the components.

Perhaps I misunderstood what you wanted in terms of control of these components. This was intended to give programmatic control over the components once they are loaded (like from the menu), and to allow you to disable a component if it is included in a combined component, for example. It was not intended to control the loading of the component, which is done via the loader.load array, nor was it meant as a means of controlling the menu settings, which is done through the menuOptions.settings object (e.g, menuOptions.settigns.explorer controls whether the explorer is loaded and enabled).

If you have a different behavior in mind, we can revisit this.

[zorkow]

Lgtm.