Bugfix, some visual improvements
-changes in Prefs.java and SimpleHttpServer.java fixes #13

Coordinator.java:
-can now explicitly restart just drivers

Prefs.java:
-savePreferences() now only write preferences to disk if they have non-null values

SimpleHttpServer.java:
-processQueryString() now private
-processQueryString() now processes keys with no value (value stored as null)
-if server should auto increment port number when starting then no port number is displayed in settings.html
-horizontal rule added after settings boxes and before buttons

index.css:
-small visual improvements