Details:

* Added support for Partition Links with a new 'zhmcclient.PartitionLink'
  resource class (and corresponding manager class). Added the following
  methods for partition links to the 'zhmcclient.Partition' class:
  'attach_network_link()', 'detach_network_link()',
  'attach_ctc_link()', 'detach_ctc_link()', 'list_attached_partition_links()'.

* Because the "Create Partition Link" HMC operation does not return the
  'object-uri' property of the created partition link, the handling of HTTP POST
  operations has been enhanced to add the URI returned in the "Location" header
  field as an artificial property 'location-uri' to the result data, if the
  "Location" header field is set and the result data does not contain
  'object-uri' or 'element-uri'.

* Added the following example scripts:

    examples/list_attached_partition_links.py
    examples/list_partition_links.py

* Added end2end testcases for 'zhmcclient.PartitionLink' and for the new
  methods addded to 'zhmcclient.Partition'.

* Added the following functions to the end2end utils.py:

    assert_properties(act_obj, exp_obj)
    skipif_no_partition_link_feature(cpc)
    pformat_as_dict(dict_)
    copy_dict(dict_)
    copy_list(list_)

* In the end2end utils.py function standard_partition_props(), improved
  the performance by retrieving the necessary CPC properties no longer
  by pulling all properties, but by pulling them selectively.

Signed-off-by: Andreas Maier <[email protected]>