add additional shared libraries (#137)

* This merge request gives the ability to add shared libaries without set LD_LIBRARY_PATH variable.

 1. Generate file in /etc/ld.so.conf.d/
 2. update /etc/ld.so.cache with ldconfig command

example pillars:

linux:
  system:
    enabled: True
    ld:
      libraries:
        java:
          - /usr/lib/jvm/jre-openjdk/lib/amd64/server
          - /opt/java/jre/lib/amd64/server

* fix format in README.rst for Shared Libraries

* Fix for #137 - change pillar libraries key to library

README.rst

         cpu:
           governor: performance
 
+
+Shared Libraries
+~~~~~~~~~~~~~~~~
+
+Set additional shared library to Linux system library path
+
+.. code-block:: yaml
+
+    linux:
+      system:
+        ld:
+          library:
+            java:
+              - /usr/lib/jvm/jre-openjdk/lib/amd64/server
+              - /opt/java/jre/lib/amd64/server
+    
+
 Certificates
 ~~~~~~~~~~~~
 

linux/system/init.sls

 {%- if system.directory is defined %}
 - linux.system.directory
 {%- endif %}
+{%- if system.ld is defined %}
+- linux.system.ld
+{%- endif %}
 {%- if system.apt is defined and grains.os_family == 'Debian' %}
 - linux.system.apt
 {%- endif %}

linux/system/ld.sls

+{%- from "linux/map.jinja" import system with context %}
+
+{%- if system.enabled %}
+
+{%- for key in system.ld.library %}
+/etc/ld.so.conf.d/{{ key }}.conf:
+  file.managed:
+    - user: root
+    - group: root
+    - mode: 644
+    - contents: |
+          {% for val in system.ld.library[key] -%}
+          {{ val }}
+          {% endfor %}
+    - watch_in:
+      - cmd: ldconfig_update
+{% endfor %}
+
+ldconfig_update:
+  cmd.wait:
+  - name: ldconfig
+
+{% endif %}