Bug 12160: Rename intranetuserjs with IntranetUserJS

Bug 12160: Rename intranetuserjs with IntranetUserJS

To match IntranetUserCSS, intranetuserjs should be renamed
IntranetUserJS.

Test plan:
1/ Be sure there is no occurrence of intranetuserjs
2/ Confirm the pref still works as before

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
NOTE: Worked before and after updatedatabase.pl, though after
      is less confusing to the person unaware of case insensitivity.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>