Clean up client config builder & improve Android/Windows client support

Hey!

I propose the following improvements to the client build|bundle|archive section:
* Combine code used for initial run and code used for later runs into a single function, *bundleClient $CLIENT*. 
* Use relative paths for *cd* and *cp* operations. 
* Instead of a single *$CLIENT.conf* file, generate a *$CLIENT.ovpn* file (as required by the OpenVPN client for Android and Windows) alongside a *$CLIENT.conf* symlink (for Linux).