www: url_helpers: Convert tag_image() to make_mysql_safe_string()
www: url_helpers: Convert tag_image() to make_mysql_safe_string()

We also make the gross_amount, vat_amount, net_amount and vat_rate
doubles rather than keeping them as strings up unitl the query
generation.

Signed-off-by: Andrew Clayton <02e0a999c50b1f88df7a8f5a04e1b76b35ea6a88@opentechlabs.co.uk>

ac000/receiptomatic