- Disable the whole group box
- Add a tooltip explaining why it is disabled
- Make sure it is disabled in the settings in case of upgrade
- Do a runtime check in case the running Qt is greater
The proxyAuthenticationRequired() signal now goes to the
ProxyAuthHandler class. That class will try to read the proxy settings
from the keychain or ask the user about them.
We won't ask the user for credentials for explicitly configured proxies.
It also does not change how the credentials for explicitly configured
proxies are stored. (see #261)
