roles/zabbix-server: Deploy Zabbix server, web UI

The *zabbix-server* role deploys the Zabbix server database, daemon, and
web interface. It requires the *apache* role to configure Apache HTTPD
to serve the web UI.

roles/zabbix-server/templates/zabbix.conf.php.j2

@@ -0,0 +1,20 @@
+<?php
+// Zabbix GUI configuration file
+global $DB;
+
+$DB['TYPE']     = 'POSTGRESQL';
+$DB['SERVER']   = '{{ zabbix_db_host }}';
+$DB['PORT']     = '{{ zabbix_db_port|d(0) }}';
+$DB['DATABASE'] = '{{ zabbix_db_name }}';
+$DB['USER']     = '{{ zabbix_db_user }}';
+$DB['PASSWORD'] = '{{ zabbix_db_password|d('') }}';
+
+// SCHEMA is relevant only for IBM_DB2 database
+$DB['SCHEMA'] = '';
+
+$ZBX_SERVER      = 'localhost';
+$ZBX_SERVER_PORT = '10051';
+$ZBX_SERVER_NAME = '';
+
+$IMAGE_FORMAT_DEFAULT = IMAGE_FORMAT_PNG;
+?>