MEDIUM: config: add DeviceAtlas global keywords

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.