Input conditions bugfixes & improvements.

Lazarus freaked out when I had set onEditingDone event for TEdit and
onClickButton at the same time and repeated onClick events, thus
sabotaging my condition mechanism. Or something like that. Not it's
finally fixed! I hope...
Also added function that tells the user that he/she didn't insert
anything, and the duplicate checking mechanism got a performance boost
(?) by not calling database stuff anymore.

The only TODO item is deleting single entry by clicking any of the 6
buttons in the layout.