Greatly improve processing time

[hugomflavio]

Main changes:

1. Detections are loaded with data.table::fread
2. Detection timestamps are converted using fasttime::fastPOSIXct
3. Substituted the for-loop for movement event creation with a more time-efficient method
4. Movement data frames are now movement data tables
5. Movement data tables now contain a Valid column, which informs the next steps of which movements should be considered for the analysis.
6. The simplifyMovements function is now obsolete, and simple.movements are created based on the Valid column of the movements, not requiring integration of the results within status.df anymore.
7. Check for detection before release has been moved to the beginning of the analysis, so the faulty detections can be removed before the creation of movement events.