RF: PDist2Target -> PDistTargetSimilarity

Few more characters for improved clarity
Merge branch 'master' of github.com:PyMVPA/PyMVPA

* 'master' of github.com:PyMVPA/PyMVPA:
  BF(PY26): define assert_is_instance for python < 2.7
  TST: unittest for @with_tempfile
  RF: use @with_tempfile to generate temporary directory
  BF: ensure that files are not matching, even if there is an "x" in the randomly generated prefix of a temporary file
  NF: unit test for afni_suma_spec
  ENH: remove "print" statement showing which surfaces where generated when adding new views to spec file
RF+NF: Rename cmd pytest -> exec; add ability to store stuff from locals()
ENH: do allow True and False for EnsureBool

This is how they look in Python so it is only native to state them as
such in environment variables and crash stating that True is not bool
is confusing to say the least