Allow symlinking when installing packages from the source repository.

Allow symlinking when installing packages from the source repository.

Now the --install option of components should be capable of completely
installing the horde stack starting with the new package.xml at
horde/package.xml down to all PEAR dependencies. Code from the
repository can be symlinked for dev mode. So this is getting nearer
to a replacement for framework/bin/install_{framework,dev}.

php horde/components/bin/horde-components --install=/srv/www/h4/.pearrc --symlink horde/horde

Currently the "Horde" role does not work yet and I assume there are
quite a few other corner cases/bugs that I will need to weed out.