Makefile improvements and corresponding doc update.

Update the top-level makefile so that we no longer have changes to
the xLights/xLights.cbp.mak file generated by cbp2make.  This moves the
few changes from xLights/xLights.cbp.mak to the top-level Makefile.
When doing a normal 'make', warnings are suppressed.  When making a
debug build, warnings are shown.  Debug build objects are also put into
the .objs_debug subdirectory so that switching back and forth from
debug to non-debug mode doesn't clobber object files.

Add a 'make debug' option to build a debug mode unstripped xLights
binary for troubleshooting.

Add a 'make makefile' option that will create the xLights.cbp.mak file
and also add xLights.cbp.mak as a dependency so it will get recreated
during normal compilation if it is manually removed.

Add xLights/xLights.cbp as a dependency of xLights/xLights.cbp.mak so
that the makefile will be regenerated if the .cbp file is updated.  If
users don't have cbp2make installed this shouldn't have any effect,
but they may not be able to compile until they get a new makefile if
new source files were added to xLights/xLights.cbp.

Add a cbp2make.cfg file to allow us to control the generation of the
xLights/xLights.cbp.mak makefile.  The only option in here currently
is one to suppress visual output of the object directory test and create
commands during each make.