add FreeSolutionNodes method for clean
change successor nodes condition

use move step instead of manhattan distance
improve the SearchStep method

use have less step node instead the same grid add before
update map file
update cost for moving
add troops type
add a new class describ troops
add a method to judge if this terrain is passable
initialize pathfindinghelper in LevelScene instead map
use level scene instead of map
change the enum type's value
add methods for pathfinding class