GPII-525 - "Speak text" adjuster group's more/less functionality is broken

Demo: prefsEditors / demos / pmt / index.html

As commented a few times across the UX mailing list, the more/less functionality in PMT was aimed to be implemented by using the expandingAdjusters functionality - https://github.com/radmanovi4/prefsEditors/blob/gpii-525/src/shared/adjusters/js/expandingAdjusters.js. However, it turned out that no more than one instance of such more/less toggler can function within the same schema.

So, I've used the conditional panel functionality, which you can see here: https://github.com/radmanovi4/prefsEditors/blob/gpii-525/src/shared/schemas/js/pmtSchema.js#L56-L61.

It's of course done by adding another boolean adjuster, related to whether the extra adjusters are visible or not (clicking more/less label toggles the bool value).

NOTE: After http://issues.fluidproject.org/browse/FLUID-5240 is complete, perhaps both implementations of more/less togglers will be equalized accordingly.