Feature Add: Security PIN support.

Lays groundwork for multi-user support but breaks the 512 function
barrier.
Recovered 1 function from DisplayScreenSaver()
Fixes for PlexInc
Converting to Multi-user
BUG FIX:
* Changed initial PIN screen to be displayed before the HomeScreen is shown instead of over it.

CHANGES
* Changed name of Preference for the pinCode

Notes:
HomeScreen really do not like other screens popping up over it too early.
Merge branch 'singluser'

Conflicts:
	Plex/source/ViewController.brs
Further changes
Removed test code
BUG FIX:
Fix PIN screen facade not getting closed correctly.

For some reason, calling .Close() from within the Activate routine would
not end up sending a isScreenClosed() message.
Merge branch 'singluser'
Continued work.  Renamed new screen to UserSelection.
Added arrow graphics
Lots of changes & Cleanup.
Cleanup of Security Pin / User Selection screens and paths.
Added background to all the roImageCanvas
Considerable logic cleanup in Security Pin and others
Small cleanups
This module holds the multiple-user support for Plex

Multi-user support is implemented by creating separate preference sections for
each user profile.  There are Reg*() routines that handle all this automatically
for you.  Just call the usual RegRead() and RegWrite() and they
will read/write to the correct preference.

The "default user" or "User 0" is special, in that the preference sections
for that user are the same as they are without multiple users.  This makes
upgrading easy.  For Users1-3, their preference sections are the usual section
names but with a "_uN" added onto them.  But again, the Reg*() routines will
handle this conversion.

Multi-user also allows a security PIN (a sequence of the directional arrows)
for any of the user profiles.

Limitations:
*   Switching users requires restarting the channel
*   User number is limited to 4.  That is a limit set by the desire to have a single
    button user selection (the direction arrows) on start-up.  That can easily be increased
    without limit with a different user selection screen.