* Fixes#1275 Transform *fields* property into array
`Include` filter takes into consideration string property
'fields' and transforms it into an array containing this string.
* Added error handling for `include` filter.
* ExecTasksWithInterLeave now contains a try-catch block
in order to catch any unexpected errors.
* LinkManyToMany now checks if *modelToIdName* exists on
*target* before continuing.
* Added unit test for *include* with string fields