New cockpit view mode (4th)

New cockpit camera mode
Ship cockpit work-in-progress
Several other modifications
Moved the SectorCache out of SectorView so it can be used elsewhere like LuaStarSystem.
missing *
Cockpit 3D shows something now (wip)
Merge branch 'master' into cockpit3d
Depth test and zero offset
Temporary solution for z-order cockpit issue
Use the sector cache everywhere possible.
Merge branch 'master' into cockpit3d
Moved creation of cockpit mesh to Ship::Init()
Cockpit lag implemented for yaw

- Cockpit lag interpolates to recover direction based on a customizable easing function and settings
- Cockpit rendering procedures moved to ShipCockpit
- Ship now updates cockpit before rendering when cockpit is available and active
- Added a few easing functions to MathUtil
- Added cockpit activation detection
Added cockpit lag for pitch
Added cockpit lag for roll
Merge branch 'master' into cockpit3d
Added cockpit lag on acceleration
Enhanced accelerated lagging
Added two missing ease-in functions
Better handling of acceleration fluctuation at max speed (less jerking)
New explotions
Add new explotion sprites