plenty of work left

slowly getting there

- figured out the save/load mechanism that won't require too much
messing around
- sorted out parts of object structure for Command/Condition trees

Move to static methods to avoid duplicating the tree structure.
Maybe these could be changed to extension methods on IProvider?

moved code from save/load classes into PlannedCommand

- filled out more of saving loading code
- changed planned command list to a dictionary holding a list of
commands for each vessel separately

- added actual command and delay handling
- not sure what to do about failed commands
- renamed ICommand to IAction and all related names

I think I figured out, how to do the internals and third party modding
support, so here it is.