Also expose print_matrix api via NonFiscalPrinter.
Also expose print_matrix api via NonFiscalPrinter.

Stoq does not use the printer drivers directly. Instead it uses a NonFiscalPrinter as a
proxy.

Expose the print_matrix api through this proxy. If the driver does not implement the
print_matrix method, the api call will be ignored.

Change-Id: I01c0c948dd0768626d377563b6adebab7dfadb32
Fixes: https://tree.taiga.io/project/stoq/task/1657

stoq/stoqdrivers,stoq/stoqdrivers