Fix for OPENDJ-800 : Support escaping characters in make-ldif templates.
The main set of changes have been provided by Elliot Kandall @ UCSF, but I've done additional cleanup of code and refactoring, added support for multiple constants per lines (this was required by the support for escaping [ and ].
Unit tests are provided and have been extended after the code review and suggestions by reviewers (CR-1401).