Add possibility to install additional packages

README.rst

 Install and configure the ``syslog-ng`` package.
 
 note: if the first character of a string is '=' the string is treated as a literal (not ecapsulated in quotes)
+
+``syslog_ng.packages``
+-----------
+
+Install optional packages which may provide additional functionality.

syslog_ng/packages.sls

+{% from "syslog_ng/map.jinja" import syslog_ng with context %}
+
+
+include:
+  - syslog_ng
+
+{%- if syslog_ng.packages is defined and syslog_ng.packages %}
+syslog_ng_packages:
+  pkg.installed:
+    - pkgs:
+  {%- for pkg in syslog_ng.packages %}
+      - {{ pkg.name }}{% if pkg.version is defined and pkg.version %}: '{{ pkg.version }}' {% endif %}
+  {%- endfor %}
+    - watch_in:
+      - service: syslog_ng
+{%- endif %}