improve error handling if user enabled bridges for a manual selected location without obfs4 proxy server
To reproduce the issue:
- disable Bridges
- manual gateway selection, e.g. to New York
- enable Bridges
An alert dialog appears saying that an obfuscated connection cannot be made. The dialog offers to use a 'plain' openvpn connection.
In case of manual gateway-selection enabled, the user should be additionally asked to change the location or to re-enable automatic gateway-selection. An additional alert action "Change location" should be added to the alert dialog. If the user taps on it they should be directed to the gateway selection fragment.