<ticket>#634</ticket>
<ticket>#634</ticket>

doc/usersguide/packages.rst: Removed spaces in sigstring and added warning

VisTrails/VisTrails,VisTrails/VisTrails,celiafish/VisTrails,Nikea/VisTrails,minesense/VisTrails,celiafish/VisTrails,celiafish/VisTrails,VisTrails/VisTrails,hjanime/VisTrails,hjanime/VisTrails,hjanime/VisTrails,Nikea/VisTrails,hjanime/VisTrails,minesense/VisTrails,hjanime/VisTrails,Nikea/VisTrails,Nikea/VisTrails,minesense/VisTrails,VisTrails/VisTrails,minesense/VisTrails,VisTrails/VisTrails,minesense/VisTrails,celiafish/VisTrails