Separate Ekos to its own headless library

This is a long term goal. It would be nice to have Ekos functionality compartmentalized to an independent library (outside of KStars) that could be linked with KStars or other applications to perform the current and future functionality of Ekos. This brings many benefits (ability to run Ekos headless) and also enables integration with 3rd party software on different platforms. One step towards this is to decouple logic and state from the GUI layer. Then to define a stable API/ABI with perhaps a plugin-based architecture.

There are some rough milestones:

1. Decouple all Ekos modules from GUI.
2. Decouple all Ekos module from KStars-dependent functionality.
3. Refactor Ekos to be plugin-based.
4. Define a stable API for 3rd party integration (including KStars, the reference implementation).