PM-740 added pegasus.transfer.threads and pegasus.transfer.sls.threads
to control the number of threads a transfer job launches. In addition,
these four parameters are handled as profiles internally. Can be
specified in the properties or in profiles

transfer.arguments
transfer.threads
transfer.sls.arguments
transfer.sls.threads

The SLS profiles are picked up from the associated compute job, in
case a user chooses to do overriding. Mainly we expect users to
control these only in the properties.
PM-740 removed extraneous whitespace.
PM-740 document the extra properites.
PM-740 document the extra profiles.
PM-740 unknown profile keys in pegasus namespace are not associated
with the jobs.