Tree h and cpp files
Changed the defintion of the graphic levels.
Removed class GraphicTask.
Uses class Task to perform the same responsibility.
Added clear function to TaksManager.
And edited some comments.
Updated some comments.
Fix fatal error.

Failed to compile! Fixed!
GameEngine is more developed.

Preparation of new map loading system.
Included XMLReader.

Namly TinyXML2.
zombie.xml

Rough design for xml file with maps and other settings
Removed Map class.
Loads windows width and height from xml.
Preparation of loading XML.

Only minor changes.
Compilation failed! Fixed!
New Test project.

It uses boost test library. No code is implemented yet.
Preparation of Unit tests.
Windows VS:
Test is executed automatically after compilation and the output is in the built terminal.
Load all data in zombie.xml.
However, none of data are so far used.
The usage of data will be implemented and commited soon.
Merge branch 'feature' into develop
New properties classes.
Will be used to store loaded xml data before the gameengine creates the corresponding game object.
Code made to load the "Base Defense Map"

But the actual loading of the <geom> code is not made yet.
BuildingPropertis can now be loaded from the xml.