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

[Ken Martin]

Thanks Tony,

I took a quick look at the init file and understand the confusion. The
settings in the init file must be set in the cache. So for example

#Build the vtkHybrid kit.
SET(VTK_USE_HYBRID ON)

Should be

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

That should do the trick. 

Thanks
Ken