REST API Example for Python Bindings

Initial version of REST API allowing minimal information about accounts, invoices and customers to be accessed in JSON format. Includes modifications to gnucash_core.py  to add additional functions.

Author: Tom Lofts <dev@loftx.co.uk>

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@22936 57a11ea4-9604-0410-9ed3-97b8803252fd