zabbix: add server frontend

zabbix: add server frontend

Added zabbix-server-frontend package, which allow to use website
interface.

To make frontend working, it is required to add some options to uhttpd
config witch allow php working.

uci add_list uhttpd.main.index_page='index.html, default.html,
index.php'
uci add_list uhttpd.main.interpreter='.php=/usr/bin/php-cgi'
uci set uhttpd.main.index_file='index.html, default.html, index.php'
uci commit

Compile tested: Yes, brcm2708
Run tested: Yes, brcm2708

Signed-off-by: Krystian Kozak <krystian.kozak20@gmail.com>