Added the revolver in the shop!

Shop update:

• With this weapon now you'll be able to shoot the thieves and with each thieve killed you get 100$ as a bonus. You still can click on the and they will just flee but killing them will give you more cash.

Horses update

• Added more horses.       
• Player can train his horses infinitely now 
• For each new horse level the training price increase as well as the training time.

UI

• Updated shop UI
• Updated some buttons UI 
• Added a tutorial in the start menu