FTAM — ftam-ftp FTF issue: login operation parameters

The login operation allows for specification of a user, password, and
account. The spec notes that account is optional. There are any number
of other login properties that affect client access to a file system
but no way to specify them.

Consider adding a property sequence to the login argument so that
optional properties can be specified. The `optional' account argument
can then be removed.

chang signature from:

FileSession login(in string user,
in string password,
in string account,
out Directory dir);

to:

FileSession login(in string user,
in string password,
in CosPropertyService::Properties props,
out Directory dir);

Change IDL for login as suggested.