Support CMake's GNUInstallDirs?

[mablanchard]

Having a quick look at the Chrono's CMake scripts, it seems like the artifact install locations (bindir, libdir & friends) are hardcoded in various places.

CMake has GNUInstallDirs: a collection of variables that let the user specify these locations (CMAKE_INSTALL_BINDIR for bindir, CMAKE_INSTALL_LIBDIR for libdir...).

Would be nice for Chrono to support this I think as it greatly ease distributors integration work.