[Cmake] Making the cmake FindXXX.cmake files more consistent

[Miller, James V (Research)]

> Consider vil (vxl's image library). vil depends on libraries such as
> jpeg, tiff, and png. We have somewhere
> 
>   TARGET_LINK_LIBRARIES( vil ${JPEG_LIBRARIES} ${PNG_LIBRARIES} )
> 
> In the executable, we have
> 
>   TARGET_LINK_LIBRARIES( myexec vil )
> 
> All works well, without the need for LINK_DIRECTORIES, because
> JPEG_LIBRARIES is defined as /usr/local/lib/libjpeg.so. That is, the
> full path is already embedded in the dependency. If it weren't, the
> client would need to do a
> 
>   LINK_DIRECTORIES( ${JPEG_LIBRARY_DIRS} )
> 
> and much of the benefit of the dependency analysis is lost.
> 

Does this impact "delivering" software?  If I ship my executable
to a customer, will the executable only look for libjpeg.so in 
/usr/local/lib? Or does the rpath thingy fix this? Or do things
fall back to LD_LIBRARY_PATHs?

Jim