Nesting abbr, wai-lang and links

This pull requests fixes nesting of abbr, wai-lang and links.
The abbr and wai-lang plugins have been modified to use non-exclusive scopes to toggle the visibility of their controls, like the link plugin already does.
This enables the user to have all controls of abbr, wai-lang and link visible at the same time for nested abbr, wai-lang and links.