ISY Version data is not passed to node server in all cases

[mjwesterhof]

The ISY Version information is obtained when Polyglot starts. We need to add logic to also trigger this when the ISY connection information is changed by the user in the Polyglot UI.

Consider the following initial setup use-case:
a) User starts Polyglot
b) Polyglot initializes with the built-in default IP address and thus cannot fetch the Version info.
c) The user enters the correct IP and credentials in the UI
d) Polyglot connects to the ISY
e) User adds a node server
f) New node server attempts to use provided version information, and gets back the value None instead of a real value -- resulting in a failure of some sort.

The solution is to trigger the Version fetch each time the UI information is updated, and to default to a valid text string ('0.0.0') instead of None, in order to minimize the potential for crashes of node servers that are expecting valid strings.