Align event based target

Refactoring changing telescope position and target setting to events instead of directly listening to the INDI properties. This has two advantages:

1. The target is explicitly set, drifting during a guiding session should no longer occur.
2. Avoid concurrency issues when accessing INDI devices

The following scenarios are considered:

• Slew to a target position through the sky map or the mount tool and call align
• Use tracking and aligning through the scheduler
• Creating a pointing model through the mount model tool
• Align without any previous slew, i.e. use the position that the mount driver reports
• Use an existing FITS image for target definition

Test cases:

• Slew to a target and align. Check if the alignment target matches the slew target.
• Drift after slewing to a target. Check if the alignment target matches the slew target.
• Successfully run the mount model tool.
• Alignment with sync only, no slew.
• Alignment to empty sky coordinates.
• Alignment with the scheduler.
• Alignment with target definition through FITS file.
• Scheduler with alignment and target definition through FITS file.