Warn user when opening direct contract link

[freeatnet]

The warning should communicate two main points:

• Trading by direct contract address means we have not vetted the token, and that the token is not officially listed
• Token contracts can be easily cloned, the user should seek verification of the token contract address from an official source

[activescott]

I am looking at this one. I am thinking to just put some warning text in in the "Other token" modal itself. Let me know if you have another suggestion.

[freeatnet]

@activescott I think the bigger issue is users getting linked to a custom address with the context of it being some coin, (CAUTION: no idea what that contract is) like so; so we probably need a prominent warning in the main interface.