Introduction of click to select and place element option in normal size screen version of molecule design and fix for heteroatom tutorial bug

Release 4.1.2

Also, a rather quick update. First, a bug found in step 7 of the heteroatom tutorial: https://www.organicchemmaster.com/MolGen/Tutorial/HeteroatomMolecule, involving adding a double bonded Oxygen to the 2,4,8,9-tetraazabicyclo[4.3.0]nona-1,3,6-triene molecule thus far created, resulted in an error that prevented the user from finishing the tutorial. This bug has been finished so the user is indeed able to create the allopurinol molecule.

Second, much of the feedback I have received thus far seems to indicate that the generally preferred method for designing a molecule is to use the click to select an element and click to place the element modality, currently in use in the small screen version. As such, I have gone ahead and introduced the click to select and click to place modality as an OPTION to use in the normal size screen version in addition to the standard drag and drop modality. This option can be selected by clicking on the drag icon in the toolbar (four arrows) to switch to click mode. Drag and drop mode can be switched back to by clicking on the icon again.

Controls: The user can now switch between the drag and drop modality of adding an element to the current molecule and the click to select an element and click to place the element modality while in normal size screen mode. This is accomplished by clicking on the drag (four arrows) icon to switch TO click mode and clicking on the arrow/pointer icon to switch TO drag and drop mode.