Token Validity and Error Reporting

[theduke]

Describe the bug

wapm login does not check that the provided token is actually valid.

When running wapm publish with an invalid token, the error message just says "You need to be logged in".

This is highly confusing. Not technical bug, but a UX bug.

[fschutt]

@theduke That design was requested by @syrusakbary in

wasmer login however does however print an error message:

wasmer login adlfjasdölfkj
Error: no user found on registry "wapm.io" with token "adlfjasdölfkj". Token saved regardless.