Change default value for authentication profile policy file

[marcocaberletti]

This PR changes the default value for authentication profile policy file. The main fixes are:

• introduction of a new file in PEP server configuration directory;
• change the default value of the authenticationProfilePolicyFile property from /etc/grid-security/vo-ca-ap-file to this new file;
• change the INI parser to fallback to this new file if the authentication profile file specified in the configuration is not readable.