Update 2.0.15 - sell all option for the merchant

- the sell all option (e.g. sell all roten apples) at the merchant was a feature requested by "grondak" on the discord server ;-) took a while to release it sorry :D
- in the in game settings the back buttons are colored green again as they should have been
- and a lot of small code improvements in the background which you wont even notice I did :D but it is cleaner now.
- removed hero brain