Implement basic Map Tile class

[krogenth]

We'll want to keep a record of all game map tiles in local memory for efficiency and better possible calculations. Each tile will be equivalent to a BWAPI::TilePosition point.

Each tile should at least keep track of:

• walkability
• buildability
• last frame seen
• if the tile has creep on it
• altitude

The tiles walkability, buildability, and last frame seen values should have getters and setters.