PROTON-328: Add hash helper function to Perl language bindings.

Added the proton.pm module to hold helper functions.

Added the following new global function:

 * qpid::proton::get_map_from - get a map from Data as a Perl hash

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1491797 13f79535-47bb-0310-9956-ffa450edef68
NO-JIRA: Fix the Perl tests for qpid::proton::Data.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1491798 13f79535-47bb-0310-9956-ffa450edef68