(legacy) fix crashreport " PHP Warning:  Illegal string offset 'ifgroupentry' in /usr/local/www/firewall_rules_edit.php on line 869"

(legacy) fix crashreport  PHP Warning:  substr_count(): Empty substring in /usr/local/www/services_ntpd.php on line 290

(legacy) fix crashreport  PHP Warning:  htmlspecialchars() expects parameter 1 to be string, array given in /usr/local/www/services_dhcp_relay.php on line 185

(legacy) fix crashreport " PHP Warning:  Illegal string offset 'item' in /usr/local/www/services_dnsmasq_edit.php on line 250"

(legacy) fix crashreport "PHP Warning:  Illegal string offset 'if' in /usr/local/etc/inc/filter.inc on line 394"

(legacy) fix some crash reports, related to " PHP Fatal error:  Call to undefined function lookup_gateway_ip_by_name() in /usr/local/etc/inc/system.inc on line 151"

fix interfaces.inc dependency for lookup_gateway_ip_by_name in system_resolvconf_generate

(legacy) from crash reports, Warning: Illegal string offset 'vip' in /usr/local/etc/inc/xmlrpc/legacy.inc on line 304

(proxy) add transparant proxy option to squid including a template for the firewall_nat rules to forward traffic to it

(legacy) add legacy_html_escape_form_data to legacy helper functions to escape array items recursive

(legacy) it feels kind of duplicate, but to avoid too much changes on how it works now let's keep the behavior approx. the same. (part 2)

Had to merge and squash and edit punctuation:

" :" to ":", " ?" to "?" to retain original document style