Custom asset design

[danfinlay]

Some plugins require custom assets. This means a few touch points in the design:

Appearing in the token list

A plugin gets to provide an asset in our "token" (now poorly named) list. The plugin gets to define the name, possibly even the icon, but we should indicate strongly what plugin this is coming from.

We can either indicate "[plugin name] asset" on each asset, or we could experiment with having a security-pattern associated with each plugin, used to visually theme its assets.

Displaying custom confirmations

Captured in #52.

We want plugins to be able to display their own confirmations for their own restricted methods. We probably want to give them a fair amount of design autonomy over these in the long term.

For security, we could constrain this to a subset of HTML/CSS for starters, but we could get some simple results with a regular iframe.

For security, we should give the user visual context over the confirmation they are seeing. The confirmation should not be able to impersonate MetaMask, or any other system notification.

There should be at least a header giving context "MetaMask Plugin [X] Notification", possibly combined with a security-pattern/image/tartan as suggested above.

Custom asset view

Captured in #103.

When selecting a custom asset, the asset plugin will want to show custom details about it.

Imagine selecting your cryptokitties in your asset list. You may see a full inventory page in your wallet, which may be enough for you to also breed them right there within the wallet.

Similarly, a layer 2 token will have special features regarding how you might like to send it, withdraw it, stake it, or any other number of things.

Because of the open endedness of this view, we probably want to render an iframe, or something iframe-like in this context. We should decide what visual indication we want to give that the selected asset view is provided by the providing plugin.