Add support for upside-down, black-white invert printing modes

[mike42]

There is an example file online here which produces buggy output, because these tools do not recognise ESC { and GS B.

$ php esc2text.php My_receipt.bin 
WARNING: Unknown command GS B
WARNING: Unknown command GS B
WARNING: Unknown command ESC {
WARNING: Unknown command ESC {
...

To fix this:

• [x] Add ESC { and GS B to parser so that esc2text can read past these commands correctly.
• [x] Add black/white invert printing to esc2html.
• [x] Add upside-down printing output in esc2html.

[mike42]

All done.