Some systems remove firewall rules, is usefull to be able to script the
reload of those rules in hooks or other custom systems.

- Resolves: #9289

http://blog.gordn.org/2015/03/implementing-run-on-login-for-your-node.html

Use sys.argv[0] as exec path instead of hardcode 'bitmask', and let
anonvpn be called RiseupVPN.

- Resolves: bitmask-systray#19

All the logic to autostart bitmask should not be vpn dependent.

The IS_${platform} constants are used in more places than the vpn
module. Let's define them in leap.bitmask.

On snap is better if we don't put stuff in /tmp but in $SNAP