U/fjammes/dm 930

This pull-request propose a feature wich enable to install only dependencies for a given product :
example :
eups distrib install qserv --onlydepend -r http://lsst-web.ncsa.illinois.edu/~fjammes/qserv

This feature is usefull for developers, before they run "setup -r ." on the product they want to develop with.

Please use :
git diff --ignore-space-change
in order to see the real code updates. Indeed, i've removed trailing whitespaces and it induces a lot of modified lines.