MEDIUM: config: add DeviceAtlas global keywords

This diff is for the DeviceAtlas convertor.

This patch adds the following converters :
  deviceatlas-json-file
  deviceatlas-log-level
  deviceatlas-property-separator

First, the configuration keywords handling (only the log
level configuration part does not end the haproxy process
if it is wrongly set, it fallbacks to the default level).
Furthermore, init, deinit phases and the API lookup phase,
the da_haproxy function which is fed by the input provided
and set all necessary properties chosen via the configuration
to the output, separated by the separator.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index 655ede0..9c78145 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -627,6 +627,18 @@
   operation. It is equivalent to the command line "-D" argument. It can be
   disabled by the command line "-db" argument.
 
+deviceatlas-json-file <path>
+  Sets the path of the DeviceAtlas JSON data file to be loaded by the API.
+  The path must be a valid JSON data file and accessible by Haproxy process.
+
+deviceatlas-log-level <value>
+  Sets the level of informations returned by the API. This directive is
+  optional and set to 0 by default if not set.
+
+deviceatlas-separator <char>
+  Sets the character separator for the API properties results. This directive
+  is optional and set to | by default if not set.
+
 external-check
   Allows the use of an external agent to perform health checks.
   This is disabled by default as a security precaution.