Rewriten to not use raspistill

Rewritten the code completely to use more direct communicatinon with the MMAL-layer and does not use parts of raspistill any more.
Threading is in place but it seems exposure of longer than 1 second is hard to achieve.
See the TODO.txt for things that remains to do.

Added gain property

Now possible to set the gain also. Seems ISO-settings does not work in RAW-mode. Use custom property "Gain" instead.

Working with FITS preview

Still a lot more to work but now the FITS-preview works in EKOS.

First kind of working version.

It can now capture raw photos in the full size mode.
Its not converting the file to FITS so preview in ekos does not work, but saving the files does.
Focusing will be very hard until at least FITS is in place, probably better to run raspistill with preview (via HDMI display) to focus now.