The DN unittest was lacking a test for i18n. The unittest was
updated to store "Hello" in Arabic with both utf-8 and unicode
and verify the values could be properly retrieved and converted
to dn string syntax.

During the testing a few problems were discovered and corrected.

* passing in utf-8 caused an ASCII decode error becuase of Python's
  silly default encoding of ASCII. The fix was to explictly use
  the utf-8 codec.

* there were a couple of places where encode/decode were not
  called correctly.

* the internal attr and value members of the AVA class were renamed
  to explicitly show they are stored as unicode.

Of course the unittest was updated as well.

Add dn.insert() and update unittest

Replace deepcopy with constructor (i.e. type call)
Can now "clone" with configuration changes by passing object
of the same type to it's constructor, e.g.
dn1 = DN(('cn', 'foo'))
dn2 = DN(dn1)
dn2 = DN(dn1, first_key_match=False)

Remove pairwise grouping for RDN's. Had previously removed it
for DN's, left it in for RDN's because it seemed to make sense
because of the way RDN's work but consistency is a higher goal.

Add keyword constructor parameters to pass configuration options.

Make first_key_match a configuration keyword.

Updated documentation.

Updated unit test.

FWIW, I noticed the unittest is now running 2x faster, not sure why,
removal of deepcopy? Anyway, hard to argue with performance doubling.

The pairwise grouping used to form RDN's and AVA's proved to be
confusing in practice, this patch removes that functionality thus
requiring programmers to explicitly pair attr,value using a tuple or
list.

In addition it was discovered additional functionality was needed to
support some DN operations in freeipa. DN objects now support
startswith(), endswith() and the "in" membership test. These functions
and operators will accept either a DN or RDN.

The unittest was modified to remove the pairwise tests and add new
explicit tests. The unittest was augmented to test the new
functionality. In addition the unittest was cleaned up a bit to use
common utilty functions for improved readabilty and robustness.

The documentation was updated.

fix test_role_plugin use of DN to avoid pairwise grouping