Update v1.40

This update includes some new commands to enable manual change of the shops stocks and prices during your game (as always check out the demo for some use examples).
I've also took care of a bug that was supposed to be gone since v1.20 but wasn't correctly crushed.
Finally, this is the first update of my plugins to include some deeper changes with a bit of a code optimisation to limit the waste of memory and a complete rework of the plugins details. Those 2 changes will also be applied to my other plugins when I'll release new updates for them.

Version 1.40 :

• New Stock increase/decrease plugin commands.
• New Set selling price plugin command.
• Memory usage optimisation.
• More detailed and organised plugin description.
• In some cases, prices could still get stucked to limit values.