Modify param discoveryByActivation to boolean

[Gozilla01]

Change discoveryByActivation parameter in gateway from string to boolean.
Use in PaperUI will be more intuitive per user, default false
The user will see this:

In the .things file this will be declared:

Bridge openwebnet:bus_gateway:mybridge [ host="192.168.1.XX", port=20000, passwd="XXXX", discoveryByActivation=true ] { }

After an experimental period, change to default = true, Issue #68