Preconfigure license & config file

Adds a new `charles::license` class which takes the parameters of `license_name` and `license_key`. This creates the Charles config file with some default settings if not present, which will pre-install the license. The class is dependent on Charles, so will install Charles before creating the config file.

Example usage:

    class {'charles::license':
      license_name => 'Your name',
      license_key  => '7ad6c7a6c87...',
    }

This also sets the following default settings:

* Mac OS X proxy is disabled by default
* Charles defaults to being maximised
* Traffic is allowed from all hosts - 0.0.0.0/0

_Note:_ an existing config file will _not_ be overwritten, so these are default settings for a fresh install.