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
Updated OpenTK to latest version.

+ changed width/height property to define client size instead of window size
Update: JSIL, opentype.js, mpg123

+ fixed GUI in particle system + shaderdemo
Output path of two projects was wrong.
Update: OpenTK*, SFML**, nunit

*there was a newer version in the official repo.
**on Windows and Linux
Changed Linux target file to work on Mac OS X, too
SFML is finally working on MAC OS X
Added openal for Linux, might be missing for a few people
Fixed a memory issue in libsfml-audio
Merge branch 'develop' of https://github.com/FUSEEProjectTeam/Fusee into develop

Conflicts:
	src/Engine/Examples/SerialisationExample/Main.cs
Merge branch 'develop' of https://github.com/FUSEEProjectTeam/Fusee into develop

Conflicts:
	src/Engine/Imp/OpenTK/RenderContextImp.cs
Submodule update.