Feature/globals (#690)

* Move global objects out of OpenSpaceEngine
 * General cleanup of main.cpp
 * Add default_joystick asset to all scenes
 * No longer suppress mouse interaction on slave nodes
 * Window delegate uses function pointers rather than subclassing
 * Fix for false overwriting of ImGUI configuration file
 * Change default color and tilt angle of fisheye rendering
 * Restructured performance manager
 * Simplify screenshot handling

modules/base/rendering/renderablemodel.cpp

@@ -28,7 +28,7 @@
 #include <modules/base/rendering/modelgeometry.h>
 #include <openspace/documentation/documentation.h>
 #include <openspace/documentation/verifier.h>
-#include <openspace/engine/openspaceengine.h>
+#include <openspace/engine/globals.h>
 #include <openspace/rendering/renderengine.h>
 #include <openspace/util/time.h>
 #include <openspace/util/updatestructures.h>
@@ -256,7 +256,7 @@ void RenderableModel::initializeGL() {
     _program = BaseModule::ProgramObjectManager.request(
         ProgramName,
         []() -> std::unique_ptr<ghoul::opengl::ProgramObject> {
-            return OsEng.renderEngine().buildRenderProgram(
+            return global::renderEngine.buildRenderProgram(
                 ProgramName,
                 absPath("${MODULE_BASE}/shaders/model_vs.glsl"),
                 absPath("${MODULE_BASE}/shaders/model_fs.glsl")
@@ -281,7 +281,7 @@ void RenderableModel::deinitializeGL() {
     BaseModule::ProgramObjectManager.release(
         ProgramName,
         [](ghoul::opengl::ProgramObject* p) {
-            OsEng.renderEngine().removeRenderProgram(p);
+            global::renderEngine.removeRenderProgram(p);
         }
     );
     _program = nullptr;