minor changes
Runs Vacuum after gui initialization.
optimization to path finding.
Use Dijkstra's algorithm to find all the shortest paths. And now
consider the floor as a weighted graph instead of unweighted.
Fix a bug. Although the vacuum can discover cells around, it shouldn't be
able to know the surface types of surrounding cells until it travers on the cell.
Battery check done!
Fix a bug in navigation logic.
Minor changes.
Fix a bug in navigation logic.
Dirt check done!
Fix a bug in algorithm.
Merge remote-tracking branch 'origin/NewPathFinding'

Conflicts:
	vacuum/src/main/java/com/se459/modules/models/Vacuum.java
	vacuum/src/main/java/com/se459/modules/models/VacuumMemory.java