WebSearch: fix for collection names with slashes

• FIX Collection names containing slashes are now supported again. However we recommend not to use slashes in collection names; if slashes were wanted for aesthetic reasons, they can be added in visible collection translations. (closes #2902)

• Adds upgrade recipe to check collection names for slashes and warn the user about them. (Soft warning only, since names-with-slashes will work more or less fine as of this patch.)

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>