Improve usage of polkit actions

Currently, both the packaged version of bitmask and the bundled version of bitmask use the same polkit action name and file. This creates a problem: if you have the packaged version installed and then run the bundle, it overwrites the polkit action file used by the packaged version.

Ideally:

• The packaged version creates /usr/share/polkit-1/actions/net.bitmask.policy
• The bundled version creates /usr/share/polkit-1/actions/net.bitmask.bundle.policy

Also, currently, the policy file points org.freedesktop.policykit.exec.path to a path inside the bundle folder where openvpn lives (now bitmask-root). It seems it would be better if the bundled openvpn exe was installed to /usr/local/bin/bitmask-openvpn and owned by root instead of living user-writable inside the bundle.

This setup does not support a multi-user system where each user has downloaded their own bundle. As an added enhancement, the bundle policy file could be called net.bitmask.USERNAME.policy, and openvpn called bitmask-openvpn-USERNAME, and bitmask-root called bitmask-root-USERNAME, but that seems like it might be more work than it is worth.

(from redmine: created on 2014-05-08, closed on 2014-06-27, relates #5634 (closed), relates #5625 (closed), duplicates #5592 (closed))