1) This converts all of our public classes into opaque pointers
and add accessor methods to "blindly" convert direct access
into accessor access. This follows more closely the CLASS RFC,
located in http://rfc.zeromq.org/spec:21.

2) All of the public headers are located in include/

3) Added versioning software number in bpm_server_classes.h

This fixes #76 github issue.
This fixes #89 github issue.