This switches swig to use python 3 specific features when generating the
bindings, switches the build over to python 3 and makes the neccesary
python 2 to 3 conversions in the bindings and tests.
It is split into
- /libgnucash (for the non-gui bits)
- /gnucash (for the gui)
- /common (misc source files used by both)
- /bindings (currently only holds python bindings)
This is the first step in restructuring the code. It will need much
more fine tuning later on.
