Camera API and documentation improvements

- getNear() and getCullingFar() now return doubles
- updated documentation
- all setProjection() calls can now throw (when enabled) and will
  do so if preconditions are not met (instead of setting a default
  projection).
- Frustum can now be logged on debug builds

samples/rendertarget.cpp

@@ -360,7 +360,8 @@ int main(int argc, char** argv) {
         const auto model = camera.getModelMatrix();
         const auto renderingProjection = camera.getProjectionMatrix();
         const auto cullingProjection = camera.getCullingProjectionMatrix();
-        app.offscreenCamera->setCustomProjection(renderingProjection, cullingProjection, camera.getNear(), camera.getCullingFar());
+        app.offscreenCamera->setCustomProjection(renderingProjection, cullingProjection,
+                camera.getNear(), camera.getCullingFar());
         switch (app.mode) {
             case App::ReflectionMode::RENDERABLES:
                 tcm.setTransform(tcm.getInstance(app.reflectedMonkey), reflection * xform);