Documentation for v0.4

[s-kostyuk]

Prepare proper documentation for:

• REST API interface
• concepts of Platform, Connection and Thing
• everpl start-up process
• a general structure of everpl and its core classes

[s-kostyuk]

In a process of writing documentation discovered a need to reconsider:

• an installation process;
• a configuration process;
• concepts of Sensors and Actuators;
• and possibly some other usability aspects.

This task is postponed until the mentioned issues will be resolved.

[s-kostyuk]

Postponed to the next version: in the next version configuration format for API is most likely to be stabilized