Add role expansion parameters for ldap/AD configuration

[guidograzioli]

New parameters to set roles in role expansion functionality allow to configure active directory as an ldap identity provider:

Variable	Description	Default
activemq_auth_ldap_expand_roles	Whether to enable role expansion functionality; if enabled, then roles within roles will be found	false
activemq_auth_ldap_expand_roles_matching	An LDAP search filter which is applied to the subtree selected by roleBase	(member={0})

Fix #188