mhekkel/libzeep: New release

The introduction of a couple new features in this release break compatibility with code written for version 5.

Among the new features are:

• removal of more boost code. Date and time routines now use the date library
• the html_controller has a new way of mapping calls, similar to what is used in the rest_controller. See example http-server-3
• new uri class
• CORS handling and option to time out JWT tokens
• and many fixes to other parts of the code