Rejection metadata for peaks

Resolves #240 (closed), #247 (closed)

Added a new enum class RejectionFlag to Peak3D which enumerates reasons for disabling a peak (i.e. setting _selected = false or _masked = false. The reason for the rejection is now displayed in the PeakTableView in any widget containing a DetectorScene. Hovering over a peak on the DetectorScene will now scroll to the correct row of the table allowing the user to see at a glance why a specific peak was disabled.

The RejectionFlag is now saved with the experiment state in HDF5 format, so it will persist when the experiment is imported from any new save created from now. Note that this breaks compatibility with existing .nsx files, meaning new test data files must be uploaded to the CI servers.