Implement plugins manager

[Lycopersicum]

Plugin manager functionalities

1. Access to LwM2M resources (IP, port).
2. Create and manage its own REST API (bound to restserver-wakaama).

Implementation of plugin manager

1. Some HTTP interface class to add abstraction layer to ulfius calls (to avoid dependence on ulfius).
2. Config class for easy variables values (such as IP address?) storage.

Plugin manager preferably should be implemented in C++, however C implementation is fine too. Feel free to edit this issue if you can clarify new features implementation.