We have a larger goal of replacing all DN creation via string
formatting/concatenation with DN object operations because string
operations are not a safe way to form a DN nor to compare a DN. This
work needs to be broken into smaller chunks for easier review and
testing.

Addressing the unit tests first makes sense because we don't want to
be modifying both the core code and the tests used to verify the core
code simultaneously. If we modify the unittests first with existing
core code and no regressions are found then we can move on to
modifying parts of the core code with the belief the unittests can
validate the changes in the core code. Also by doing the unittests
first we also help to validate the DN objects are working correctly
(although they do have an extensive unittest).

The fundamental changes are:

* replace string substitution & concatenation with DN object
  constructor

* when comparing dn's the comparision is done after promotion
  to a DN object, then two DN objects are compared

* when a list of string dn's are to be compared a new list is
  formed where each string dn is replaced by a DN object

* because the unittest framework accepts a complex data structure of
  expected values where dn's are represeted as strings the unittest
  needs to express the expected value of a dn as a callable object
  (e.g. a lambda expression) which promotes the dn string to a DN
  object in order to do the comparision.

The changes include:
 * Change license blobs in source files to mention GPLv3+ not GPLv2 only
 * Add GPLv3+ license text
 * Package COPYING not LICENSE as the license blobs (even the old ones)
   mention COPYING specifically, it is also more common, I think

 https://fedorahosted.org/freeipa/ticket/239

Fix a logic problem in ldap2:get_schema() for determining if it
can fetch the schema or not. Normally we only want to do this for servers
but if you pass in your own connection it will use that.