config: introduce controller 'id' and 'network_id'
Following config options are introduced -
- id - Controller ID (or 1905 AL-macaddress of the Controller).
- network_id - unique identifier of the Multi-AP network managed by this Controller. When not present in Controller's config, gets auto-generated and saved to config. E.g. option network_id '26787168-f5d3-11ee-8fc7-ac919bb703e8'