Add support for the brl:render attribute
Add support for the brl:render attribute

i.e. render dtb:em, dtb:strong and brl:emph depending on the
brl:render attribute using quotes, singlequotes, emphasis or ignoring
them altogether.

sbsdev/daisyproducer,sbsdev/daisyproducer,sbsdev/daisyproducer,sbsdev/daisyproducer