Previously, the meeting class was determining Dialable based on a meeting ID being "0". This is a Zoom-specific thing, but it has recently become a thing for Cisco codecs to have meetings that aren't necessarily dialable. Adding this property to the `Meeting` class allows the specific codec type to set it correctly based on that codec's needs.
In order to support the way some Smart Objects work, a clear
directory join was needed in order to allow for clearing a
selection in certain circumstances.
In order to support finer-grained dependencies while
developing plugins, the Development Device Factory was added.
