Improved buildings gui, internal structure (#29)

Now it's easier to add buildings to building panels . They are
positioned automatically and also get their name and icon from the
buildingtype.
Major Gui refactoring

The gui is now much more structured and it's much easier to add building
categories.
Improved street deleting (#27)

Streets can now be deleted by dragging over the street you want to
delete.
 On branch Benedikt
 Changes to be committed:
	deleted:    src/game/BufferTools.java
	modified:   src/game/Grid.java
	modified:   src/game/GridCell.java
	modified:   src/game/Main.java
	modified:   src/game/ResourceManager.java
	modified:   src/gui/BuildingPanel.java
	modified:   src/objects/BuildPreview.java
	modified:   src/objects/Entity.java
	new file:   src/objects/Mesh.java
	deleted:    src/objects/Model.java
	modified:   src/objects/ObjectLoader.java
	modified:   src/objects/Streets.java
	modified:   src/objects/Terrain.java
Improved the AnimationManager

The AnimaationManager now accepts custom values and times as parameter.
This is also used for smoother camera animations.
Added custom finished action to AnimationManager

When a custom value is used, a method finishedAction() can be defined,
that is called when the animation finishes.
Merge pull request #34 from ForceField-IndieGames/Benedikt

Gui refactoring, better street deleting, improved AnimationManager
Tweaked camera zoom
Added placeholders to language files

Language files now support placeholders like %1%,%2%... which can be
used to fill in information.
Bugfix: City saved with wrong name (#35)

The cityname defined in the textfield was not used when saving the city.
Optimizations & Refactoring

Buildings can now have their own class. Also, buildings have click
events.
The size of save files was reduced by 50%.
Bugfix: Particles not rotating correctly

Particles did not rotate to the camera in certain angles.
Implemented citizens (#33)

Houses and big houses now slowly get inhabitants after they are built.
The citizens that lived in a house are removed when a house is deleted.
Merge pull request #37 from ForceField-IndieGames/Benedikt

Citizens, optimization, bugfixes
Bugfix: load and settigns buttons (#36)

The load and settings buttons in the main menu now work correctly
Bugfix: Citizens in buildings were not saved (#38)

Only the total amount of inhabitants was saved. That lead to double
citizens when loading a city.
Bugfix: more citizens while pausing or new game

The number of citizens went up even when the game was paused or  a new
game was started.
Minor changes to the BuildingTask
Added gui for building information (#9)

When a building is clicked a new panel shows up with further information
about the building.
Bugfix: camera moving up while building (#42)

When buildings were built before the camera wiggle animation was
finished, the cameras Y position permanently changed.