* Update button when the name of a connected route changes
* Indicate partial internal connections (previously only the
client name ("ardour") was displayed.
* Escape markup in I/O plugin and client names
* Refactor code, use a common base-class for route and
route-less I/O Buttons
This fixes an issue with the connection button still showing
the name of a Bundle even after deleting it, or displaying an
old name after renaming a bundle.
