Defines control, start/stop, Rclex.SubLoop functions.

Subscriber itself can be created on Node by calling below,

• Rclex.Node.create_subscriber/3
• Rclex.Node.create_subscribers/4

There are 4 GenServers including this module itself under the Node. They work together as shown below.

+-------------+
| Rclex.Node  |
+-----+-------+
      |
      |
      |
      |                            +-------------------+                            +-------------------+
      +------Supervisor------------+ Rclex.Subscriber  |------Supervisor------------+ Rclex.SubLoop     |
      |                            +--------^----------+                            +--------+----------+
      |                                     |                                                |
      |                                     |                                                |
      |                                     | GenServer.cast to Rclex.Subscriber             |
      |                                     |                                                |
      |                            +--------+----------+                                     |
      |                    +-------+ Rclex.JobExecutor |          GenServer.cast to JobQueue |
      |                    |       +--------^----------+                                     |
      |                    |                |                                                |
      +------Supervisor----+                | GenServer.cast to JobExecutor                  |
                           |                |                                                |
                           |       +--------+----------+                                     |
                           +-------+ Rclex.JobQueue    <-------------------------------------+
                                   +-------------------+                                      

• This module stored call_back to be executed.
• Rclex.SubLoop triggers the call_back execution according to pushing message to Rclex.JobQueue.