Feature: Use default path of /etc/rc.conf

[gyptazy]

General

Mostly this tool will be used for validating a modified /etc/rc.conf file. Therefore, this should be the default path when not using any arguments. However, it should still remain able to validate instance copies.

Tasks

• Set a default path to /etc/rc.conf when not called with an argument as path
  • Validate that the default file really exists (it might still get called on other systems and should provide a correct error message)