added the code in map functions that ignores deleted trashed datums
fixes implemented the function to trash datums. Trash button on datum marks the datum's validation status Deleted and remove it from the datum view. For now the deleted datum still shows up in the datalist though."
changed delete-button to trash-button
added putInTrash fucntion in Session and Corpus
corrected the function names
added putInTrash function in datalist as well. the function is doing something not quite right in at least session and datalist. clicking the trash button erases all the session or datalist names from the list in corpusreadview. #797