Tidy up "firewall_rules.php" XHTML

Close INPUT, BR and IMG tags and add ALT to IMG tags
Deprecate the ampersand in ANCHOR tags
Move NOWRAP to class statement
Add missing closing FONT
Add missing opening and closing TR tags
Add CDATA sections to SCRIPT tags
Merge pull request #549 from ExolonDX/branch_16

Tidy up "firewall_rules.php" XHTML