Change default cache folder to /var/lib/bithorde

[bithorded/server/config.cpp]Change cache dir behavior, if not specified it's inactivated.
[debian/bhfuse.upstart]Check if mount point exist, if not create it.
[debian/bithorde.postrm]Remove bithorde socket when the package is uninstalled.
[template.config]New default values and some format clean up.