Allow operation when no registry is available

[jacogr]

• Allows the display of native network balances even when Tokens are not available, Fixes https://github.com/ethcore/parity/issues/2975 (Registry -> TokenReg)
• Remove built-in dapps when no registry is found, Fixes https://github.com/ethcore/parity/issues/2979

[ngotchac]

There seems to be some errors when there is no Registry contract address (_retrieveTokens Error: -32602: Invalid params or Error: -32602: Invalid params(…) in ws.js). I guess some part of the app is not checking if there is actually a registry deployed.

It also seems that my local dApp which doesn't uses the registry isn't displayed/accessible.

[jacogr]

Ok, the local dapp should definitely show, that needs to be addressed - only builtins should be removed.

The intent was not to remove the actual check from all places, just made sure that when they fail, they are ignored. (There are a number of combinations when done properly, no Registry, Registry but no TokenReg, etc.)

[jacogr]

As discussed & shown, cannot replicate the dapps issue. Others issues not for this release, could do it straight-after.

[ngotchac]

My bad, it is working...