added user interfaces and utilities that enable experiment data download from machines that have ssh access to the storage host

fixed few issues found while testing gridftp plugin and file observer; made observer more generic by shifting some functionality to agent

refactored utilities; use classes from common area wherever possible; added web service notification when experiment users get notified

added DB and DS web service interfaces for deleting user experiment role; added new delete-user-experiment-role command

introduced interface for notifying ds service to update experiment users; fix bug in linux experiment utility