JCR-2113: Writing access control

This patch addresses the following as indicated in https://issues.apache.org/jira/browse/JCR-2113:
a. adjust jcr2dav module and make sure the RepositoryConfig gets a valid ac-provider configuration parameter set
b. complete setPolicy, Batch#setTree, + testing
c. complete removePolicy for jcr2spi and complete implementation for removal of protected items on jcr-server.

did you see... they are passed as parameters when creating the client repository object. the previous impl only uses the davex uri and the config for the access control providers were missng. the second is added as an init param to the servlet. or maybe that's not what you mean?