add Genome::Sys::touch
add Genome::Sys::rename

CORE::rename preserves permissions, uid, and gid even though we might
not want to.  GNU 'cp' does not, by default, preserve these attributes
but also causes more IO. Genome::Sys::rename is meant to be an
alternative to CORE::rename that does not preserve these attributes.
convert touch and rename to class/package methods instead of functions
add test for touch and fix atime/mtime not being updated