Optional support for hovercrafts, cars and missiles and fix of #79,80,81

Optional properties for hovercafts with default values:

all these properties have effect only to translation, not rotation of the craft.

canHover: false           # boolean  if it will check hovering 

hoverLimit: 0               # int 0 is perfect for cars, its used when canHover or useGravity - it make step only over one 
block (don't use too big numbers! each number means one (with useGravity - two) translation check process!)

harvestBlocks:              # destroyed blocks (array of strings, default empty)
  #f.e:
  - LONG_GRASS
  - DOUBLE_PLANT
    #add flowers etc.

useGravity: false            # boolean - try to go one block down each step of move (it checks hoverLimit count layers 
under craft , independent on canHover)

canHoverOverWater: true    # boolean - prevent hovering over water (it checks hoverLimit count layers under craft)

moveEtities: true            # boolean - if false, it prevents kamikaze and rocket drivers and causes release craft after cruise activation


corrected minHeightLimit and maxHeightLimit to 0 and 255, maxHeightLimit can be now same as minHeightLimit 

bug fixes:

 #79 (partial fix - only when moveEntities: false) ... when moveEntitites: true - there is still problem with activation from outside of the craft that isn't recognize as craft-leaving-event sometimes.

#80, #81 - same bug, fixed