When cloning a Git repository that contains symbolic links to a file
system that does not support symbolic links, Git replaces the links with
plain text files that contain the path to the target file. If we encouter
such files, install the linked source file rather than the link.
Rename install.sh to setup.sh in order to take the Makefile targets.
Former make target names are now passed to the script like
$ ./setup.sh uninstall
Fixes#45.