All Mist/Wallet data should be stored per-network

[hiddentao]

All account, contract and other should be associated with a network when being stored within Mist's internal data stores (whether Meteor or backend). This way when the network is switched it is able to cleanly load in the appropriate data for the new network.

[luclu]

This could also improve the situation on these ones:

• Backup menuentries always redirect to default main-net geth-data-directories
• Mining menuentry only works on test-net (no private-net) and if mist is in control of geth session

[luclu]

Network-Id query:

$(which geth) version | grep -m1 "Network Id" | awk '{print $3}'

or via regex:

(?<=Network Id: )\d+

[hiddentao]

At the moment we use the genesis block id to figure out which network the user is on, see https://github.com/ethereum/mist/blob/develop/interface/client/templates/elements/networkIndicator.js#L21.

I propose keeping to this mechanism as it's more reliable than network id (a Geth user could startup Geth and set networkid to whatever they want, e.g. especially if they're simply running a local private network).