Progress on version 12

Our main devlog can be found on wordpress: https://theairlineproject.wordpress.com/

But the main things which have been implemented so far for version 12 are:

• Condition Levels for aircrafts and the possibility of sending them for maintenance
• Tool tips for buttons
• Better options when ordering aircrafts
• Quick assignment of aircrafts to routes
• Converting aircrafts to cargo aircrafts
• Quick replacing an aircraft with another