Did I do this right so far? What next?
I grabbed the new dimmer binding and (per suggestions in thread) uninstalled the Wemo binding from PaperUI. Then restarted openhab. Then copied the .jar file into the addons directory (/usr/share/openhab2/addons/).
Perhaps unnecessarily I changed ownership from root to openhab for user and group on the jar file once it was copied. (??)
Restarted openhab again.
Bundle:list showed it was “installed” but not “active”.
I tried to start it (bundle:start 184) and got an error:
Error executing command: Error executing command on bundles:
Error starting bundle 184: Could not resolve module: org.eclipse.smarthome.binding.wemo 
Unresolved requirement: Import-Package: org.eclipse.smarthome.io.transport.upnp
The problem seems moderately clear. I need to install something that is not installed (for some reason). Should I install this via PaperUI (how?) or do I drop another .jar into the addons/ directory (and where do I find it?)?