Fix Apple Mail email header encoding bug

Apple Mail adds quotes when encoding email headers (`From`, `To`, `Cc`), e.g.:

```
From: "=?iso-8859-1?Q?Boss_H=FCgo?=" <hugo@boss.com>
```

But the python email module does not support this. This patch removes the quotes in this very specific situation so that the python email module can decode the header value properly.
I've updated the an encoded from header in a test-asset and did not add a specific test - this covers various areas of ftw.mail code.

The Pull-Request also includes minimal view tests.

@lukasgraf 
/cc @maethu