Update #71 - Minor update (tractor fixes)

This update attempts to fix a few issues related to the tractor changes introduced yesterday.

Bugfixes:

• Fixed wrong tractor behavior when fuel is almost empty.
  
• Tractor now starts automatic mode a tad slower for half a second. This should avoid skipping some work steps on the first row of tiles.
• Added a special behavior for automatic tractor when visiting a farm with medium-high ping. This should help with potential high-ping issues with auto tractor.
• Added some checks for potential issues with auto tractor and really low framerates.