Refactor update rates of tab controllers

Previous way of controlling when controllers were run was split among
the different controllers, meaning that third parties would require
knowledge of internal state of controllers in order to be on the same
update schedule as them.

This refactor moves the logic into a seperate class.

Additionally, it also stops the use of the `adjustUpdateRate` function
on all tab controllers, since it broke the prime-number-ability of
less collisions.

src/tabcontrollers/SteamVRTabController.h

@@ -49,10 +49,6 @@ private:
     bool m_cameraRoom = false;
     bool m_cameraDashboard = false;
 
-    unsigned settingsUpdateCounter = 0;
-
-    unsigned int m_steamVrSettingsUpdateCounter = 97;
-
 public:
     void initStage1();
     void initStage2( OverlayController* parent );