Add an "Unknown" event type for sections when discharge history is unclear

[AlexLipp]

Currently, if a sequence of Alerts is reached which "makes no sense" (e.g., a "Stop" followed by another "Stop"), we simply ignore the alerts. However, this by default, then means it is displayed or described as "not discharging" which is erroneous. Instead, it would be preferable to display it as a new type of "Unknown" event type starting from when the discrepancy first appears and ending when it has finished. Inspecting the logs, these events are rare and do not make up a significant period of time. Nonetheless, it would be beneficial to better reflect this edge case.