[sldev] Default FOV/FOV slider bar in graphics

[Feilen]

I think that lowering the default FOV (field of view) whenever using SL 
makes it much more immersive, however it always resets back to the 
default. Could there be a way to keep the FOV when restarting SL or even 
a slider bar in the graphics tab? That would be much better for those 
with HMDs with a set FOV, which is much lower than the default (the one 
I'm planning on obtaining is 32°).