[Cmake] feature request - separate user and system cmake cache files

[Ken Martin]

Hey Tony,

Actually to provide some more input on init files... there are a couple
other cases I can think of:

1) there might be an existing cache and you want to force the cache
values to be set a certain way. For example say you want to turn Hybrid
on even if the user has previously run cmake and turned it off.  Then
you can do:

#Build the vtkHybrid kit always.
SET(VTK_USE_HYBRID ON CACHE BOOL "doc" FORCE)


2) another option is that you want to set and then hide options so the
user will not be tempted to adjust them later on.  Then

#Build the vtkHybrid kit always and don't distract the user 
# by showing the option.
SET(VTK_USE_HYBRID ON CACHE BOOL "doc" FORCE)
MARK_AS_ADVANCED(VTK_USE_HYBRID)

Ken