Enhance Principal Mapping to Handle Dynamic Mappings

We will add the ability to use provider parameters in order to dynamically create a disambiguated username for use in the Hadoop cluster.
This will require unix accounts for the disambiguated name inside the cluster.
The mapping syntax will be something like the following to dynamically append a domain/tenant id to the username:

<provider>
    <role>identity-assertion</role>
    <name>Default</name>
    <enabled>true</enabled>
    <param>
        <name>tenant.id</name>
        <value>_domain1</value>
    </param>
    <param>
        <name>principal.mapping</name>
        <value>*=_PRINCIPAL+$tenant.id</value>
    </param>
</provider>

The above demonstrates using a dynamic method of adding a tenant.id as a suffix for disambiguating users for this topology from users of another. Reversing the order of that idea would provide a prefix. This generic parameter name approach is very flexible.