problem: there are many options and we do not autogenerate their handler functions

* CZMQ has a large number of options for zsock's, with repetitive code for them, and CZMQ handles this by using gsl + a model xml file for generating this code.  
* I've added a modified sockopts.xml file + gsl templates for generating socket option code
* Some options are not handled yet (specifically key options) but this is a large enough working change that I feel it should be checked in before more work is done on it.