first step for OnCollision is made

TODO: Passing Event from RigidBodyImo to RigidBody.
TODO: OnCollisionEnter, OnCollisionStay, OnCollisionExit id possible
Updated BulletSharp.dll to Veriosn 2.82
renamed Bounciness to Restitution, added Drag
cleaned up, BulletSharp Example deleted.

Take a look at the BulletTest Example-Project if you're interested in an
exmaple for physics in Fusee
Added Gravity Method to DynamicWorld, some work on the CollisionCallback stuff
added the possibility to optimize ConvexHullShape for better performance
fixed CollisionShape Class
cleaned up some code
Merge remote-tracking branch 'origin/develop' into feat_physics

Conflicts:
	src/Engine/Examples/InputDevices/Assets/Teapot.obj.model
	src/Engine/Examples/InputDevices/Assets/world_map.jpg
	src/Engine/Examples/InputDevices/InputDevices.csproj
	src/Engine/Examples/KeyframeAnimationTest/Assets/Cube.obj.model
	src/Engine/Examples/ParticleSystem/Assets/Face.obj.model
	src/Engine/Examples/PhysicsTest/App.config
	src/Engine/Examples/PhysicsTest/Main.cs
	src/Engine/Examples/PhysicsTest/Physics.cs
	src/Engine/Examples/PhysicsTest/Properties/AssemblyInfo.cs
Set up Gui to show fps while running physcstest
cleaned up
Final fixes for Thesis Final Example
Added $(SolutionDir) definition.
Updated Fusee_Linux.targets
Added libfreetype and mapping config -> GUI works
Updated/Improved AppBrowser to work with all examples.

- removed unused assets
- referenced necessary dlls
- disabled search for .dll (slow and unnecessary?)
- "loading..." text ressource
- RenderCanvas' UnLoad() is now called
- other way of forcing garbage collection
- setting the size without border size
- draw update to redraw background image
Added Dispose() to Input/Audio/Network/Time

We need to set some singleton instances to null when closing the
application.
Fixed the spotlight in the shaders and added a simple color shader for DebugLines
Changed parts of SceneManagement

This was necessary because we can't set the singleton instance to null
when closing the application.

- not static anymore
- children need to be set explicitly
- a lot of ReSharper stuff
- cleaned and improved the 3 examples: SolarSystem, KeyframeAnimation
and LightTypeTest
- removed unnecessary assets
- resized the skybox texture (6mb was too big)
Added all examples to the AppBrowser