[IMP] Add support to ESC/POS check slip printer

Hello,

This is a first step (of a WIP) to add support to ESC/POS Check slip printer on the Point Of Sale, (tested on a EPSON TM-H6000IV).

The code which transforms XML to ESC/POS commands is not extendable that's why we proposed a merge for adding this printer capability and avoid code duplication.

Comments are welcomed!

Regards,

Sylvain