split main class and external API

Cloubed class has been put in a separate file so that all functions of the
external API are alone in their own dedicated file.
changed IP network in example centos based cloubed

The IP network in the example of centos based cloubed has been changed from
10.5.0.0 to 10.6.0.0 to avoid conflict with debian based cloubed. Now, both
provided examples can be instantiated in parallel.