Add example of custom CMake output directories

Use CMAKE_<TYPE>_OUTPUT_DIRECTORY_<MODE> variables to configure
output locations of build products for both single and multi
config build tools. Use GNUInstallDirs to provide the basic
structure of installation directories, and map build output
directories to these.

Build dummy executable, shared and static library targets to check
locations are used appropriately. Provide output in exe and interfaces
in libraries to report build mode used to compile them.