testMaker Code

Fixes SF #2003120;

Fixes SF #2003096; Validate order does not reorder when nothing's changed.
Changed core/types/TestStructure.php to satisfy validateOrder function;

Fixed error when adding item display conditions with displaying of more than one items per page in the parent block; (See SF \#1979369)

Updated FPDF to version 1.53

Change some error messages and spell mistakes.

Change the file type checking and fix spell mistakes.

Change error message.

Improve the error handling with logo upload.

Default duration field of new test runs to 0 to prevent migration script from
triggering for new test runs.

Prevents special users from being disabled (reported as SF#2003116).