Ability to swap two presets when organizing banks

[altarofwisdom]

In the original Virus Editor dragging a preset onto an other would by default swap them, which is a time saver when reorganizing them, and avoids mistakingly overwriting a preset

Having different behaviors depending on what modifier is held while dragging:

• no modifier: swap
• option/alt drag and drop: overwrite target

Keep up the great work !