add ldap user info object that will be used for ldap-based utilities; introduce ldap create user functionality

changes to sftp utility to allow calculating md5 sum, as well as to be able to use ssh key for authorization

reworked catalogging to use collection on a per experiment basis; removed generic apis for retrieving files

added new polling observer agent; enhanced upload functionality to avoid resource starvation with simultaneous daqs and uploads; resolved issue with starting uploads with large number of files in the specified directory