integrate snowflake over tor for api communication

As a first little step towards snowflake support for the API communication, we want to use tor's ability to obfuscate and route traffic via snowflake.

• for now we're integrating a static tor binary, wrapped into a nice Android-API: https://github.com/guardianproject/tor-android
• API comunication over tor/snowflake should only be done if the VPN is not running.
• if the initial bootstrapping fails, we should run tor. If so we should inform the user that we'll use tor/snowflake in order to fetch the API data
• in order to use the snowflake client we need to cross-compile it using gomobile
• adapt the CI to build tor binaries and snowflake