Export feature now exports between start and end dates

Updated:

  - Improved LogfileLoader to properly seek to timestamp
  - Add functionality to LogfileLoader to seek-ahead to latest timestamp
  - Export now exports up to 23:59:59 of endDate instead of 00:00:00
  - Misc clean-ups and improvements

To do:

  - Save dialog states on device configuration changes (rotation)
  - Use string resources instead of hardcoded strings
  - More misc clean-ups and improvements