Update 0.3.5

List of changes:

• Added new tab "Classes" under "Students" tab - where you have an overview on all your classes.
• Created class grades from 1 to 3.
• Added ability to move between lesson plans for different classes while assigning lessons.
• Now students can finish their classes and move to next class every year or leave your school after 3 grade.
• Added ability to remove or add new class.
• Now each class has a student limit.
• Added new texture to paint: Dark wood.
• Now NPCs are moving at their free time instead of standing in the corner of your plot.
• Smaller fixes and changes.