Fixed path for doc build.
Fix doc path issues (hopefully)
Added writeonly param to all property factories
gpib wrapper changes: removed strip, added timeout spam and improved v5+ support
Added HP3456a System Multimeter
Rewrote HP3456a to use writeonly bool and enum_properties

- removed private members that shadowed parameters set on the hp3456a
- added "setter" documentation to "getter" properties for sphinx
- added HP3456a to sphinx apiref/hp.rst
- removed a gi_gpib.timeout bug