Faster sorting of elements

Add trigger_offset_ns to overall delay.

- Removed segment_container append(), slice_time(), last_edit
- Improved performance of looping arguments
- Improved performance of segment_container.reset_time()
- Improved performance of segment and segment_container indexing
- Improved performance of sequence pre-rendering
_ Reduced memory usage
- Added sanity checks on looping arguments
- Fixed addition of 2 segment_containers to construct simultaneous driving