Settings: MEDIA VOLUME STEPS CONTROL

Adds ability to control media volume steps control
I found it there's no media volume steps control.
some user use 30 steps or etc.
  It's bothering some peoples when decompliing/compling framework.jar to change volume steps
So I made this function
SUPPORT:
       15 (Default)
       30
       45
       25

I'm a noob coder, so this way can be totally wrong.
but I tested and it's fully working!
When you change media volume steps
Your phone will be reboot.