Signer new-token generates a link and opens browser

[tomusdrw]

Closes https://github.com/ethcore/parity/issues/2874

[rphmeier]

Have also had a few requests to put the code on its own line to make it easier to copy

[gavofyork]

moving in the right direction here.

since it now opens a window, let's just have the user run parity open rather than parity signer new-token?

[tomusdrw]

So I think we should rather:

1. Remove parity signer new-token
2. Have parity ui open UI with newly generated token each time
3. But we also need to keep track of token creation date and number of times it was used
4. Remove old tokens that have never been used.

[jacogr]

UI code to handle the auth token as passed forthcoming in this PR.

EDIT: UI handles #/auth?token=valid-token-here path correctly - if token setting fails, the same usual connections fallbacks are still in-place (in this case we expect to never get there)

[tomusdrw]

1. parity ui runs parity, generates new token and opens up a browser with UI (in case parity is running it just opens a browser)
2. parity signer new-token generates token, opens browser and quits.
3. We track creation time and usage of tokens.
4. Tokens which were never used and are more then a day old are removed.

[gavofyork]

parity signer new-token generates token, opens browser and quits

so a user doesn't care about authorisation tokens - they only care about using parity's UI. if this opens a browser window, it should be called parity open or some such. keeping it with the present name:
a) confuses any power-users that expect it just to create a new token; but way more importantly:
b) is a really obscure command for actually opening a new window.

[tomusdrw]

parity ui - opens a browser with new token in URL (starts parity if not running already)
parity signer new-token - displays the new token (and link for convenience) and quits