cmake: sorted files in EBLOB_SRCS
data-sort: use exlicit data-sort unless EBLOB_AUTO_DATASORT is set

This will prevent data-sort from running when developer/sysadmin is not
expecting it.
Also simplified datasort is_sorted/schedule_sort API and removed
DATASORT build time define.
defrag: enable timed-defrag
defrag: re-enable defrag