Use network ID instead of URL to identify faucet network

[mvadari]

The logic determining which faucet to use currently guesses based on the text of the URL of the node the user is connected to. This isn't very robust, as it means if a user is connected to their own node or using an IP address directly, then they need to enter the faucet URL themselves.

We can instead use the network ID of the network the user is connected to, which should always be the same regardless of what node they are using.