Fix include directories in example plugins
Find GLFW in source builds on Linux
Fix compilation for gcc 4.9.1 on Linux
Compromise for GCC 4.8.2
Remove quotation marks as they confuse cmake
Remove Dummy widget.
Add screenshot widget.
Merge branch 'master' into feature/screenshot_widget
Merge branch 'feature/screenshot_widget'
Fixes Compile errors

* missing include (because of missing include directory link in cmake)
* wrong initialization order (causes compile error on my gcc 4.8.3
  linux machine)
Fixes cmake policy CMP0028 (Qt5::OpenGL missing)
Merge pull request #36 from lordgeorg/compile-fix

Fixes Compile errors
Merge pull request #37 from lordgeorg/cmake-policy-fix

Fixes cmake policy CMP0028 (Qt5::OpenGL missing)
Merge branch 'master' into navigation

Conflicts:
	cmake/PlatformLinuxGCC.cmake