Add options to set file type or embosser model, character table and page format

These options will be used in addition to `output-file-format` to determine the conversion from PEF to the final result. (Compare with how `braille-code` was split off from `transform`).

To specify the page format, several options might be needed. This information, together with the existing `page-width` and `page-height` options, will be used to determine the available rows and columns.

If both an absolute page size and a number of rows/columns (`page-width` and `page-height`) is specified, we try to respect the rows/columns setting if possible, and position the page on the physical page in an appropriate way.

If no information is given through options, the system could fall back to determining the page format based on the CSS (`@page` rules).

If needed, the CSS to OBFL conversion should adjust the formatting based on the printable page area for the given embosser (with warnings).

If the paper size has been computed from the specified number of rows and columns or from the CSS, this information should somehow be conveyed to the user (so that he can make sure the right paper is loaded in the printer).