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

    release 0.13 from tag 20160527

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

    release 0.11 from tag 20160429