Increased multi-user to 8, cleaned up Registry functions, misc tweaks and bug fixes

Changes:
* Multi-user increased from 4 to 8 user profiles
* Removed the Reg*ByUser() functions and just extended the RegRead() and RegWrite().  Results in much cleaner code and easier maint.
* A couple of minor bug fixes including being stuck in the PIN entry and the background items
* Misc tweaks to wording and some 

Note: I never mentioned before, but this is untested on SD screens.  I only have a Roku 3.