Implement pre-loading for .sdt files in the interest of performance as an option.
Extend pre-load option to allow smaller sub-planes & address format issues.
Further format issues.
Split initialisation of channel & time bin into preLoaded & not.
Merge pull request #897 from melissalinkert/rebased/develop/dev_5_0

Implement pre-loading for .sdt files in the interest of performance. (rebased onto develop)