JCR-2113: Writing access control

This patch addresses the following, as described 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 partial implementation for removal of protected items on jcr-server.

add the protected-handlers config properties file to the deployment descriptor(web.xml). this is where the JcrRemotingServlet will look to located protected item-remove handlers. does it makes sense to configure this in the deployment descriptor?