[Tagging] Feature Proposal - RFC - value 'basic_network' - Tagging with a simultaneous basic network, node network and/or route recommendation

[stevea]

(Although cycle_network=DE:basic_network, or cycle_network=DE:BV:basic_network, or cycle_network=CH:basic_network... are values that are "more harmonious" with the methods by which the rest of the world have chosen to assign values to this key).