Improvements to Viewports

This user story contains issues related to viewports. Bug QT3DS-370 reported multiple issues:
There is lots of weird functionality in perspective viewport navigation, and many missing features for it to be usable.
Navigation controls. ( remove functionality of changing manipulator mode with Ctrl and Alt )
Navigation controls. ( Create Alt + click based navigation)
Missing World axis helper, so you will get lost in the viewport ( top right corner of attached image )
Missing Grid ( No way to visually compare size and distance between objects )
Deselecting object. ( clicking to empty space in view currently does not deselect the selected object. )
Background gradient. ( Background color should be gradient, to avoid solid color graphics to disappear in viewport )
Camera preview to perspective view ( boolean to control between layer/all layers mode )
Camera object in perspective view ( no way to see what direction camera is looking )
Light objects in perspective view ( no way to see range of pointlight in viewport etc.. )