Added ability to adjust min/max melee, height and detection settings

These changes bring more flexibility for the user to customize the
programs settings to suit his farming environment. The changes made
were:

* Addition of a misc settings view and view model to change max / min
melee distance, max detection distance, max height difference.

* Addition of a new MiscSetting's class to hold the data and is placed
in config within the engine.

* I've also renamed the file Session to FFInstance to match its class
name.