Patch v0.15.1

Fixed some issues found by @Gigantoherceg, @Pietrus1745 and @olafoertelt,

[h2]Release notes v0.15.1[/h2]

[h3]Features:[/h3]

• staff cell will be marked if worker is not yet assigned to any building;
  

[h3]Changes:[/h3]

• reworked main menu a bit;
  

[h3]Known issues:[/h3]

• game stuck when pressing "Continue" button in the Main Menu after all saves were deleted;
  
• wrong description for "Turn on lights" contract;
  
• missing param in the description for "Put spacecraft into geostationary orbit" contract;
  
• improved base tutoril step where you turn on engines after time warp, so engines will explode less frequently;
  
• wrong parameter for "Leave Earth's SOI" contract.