Separate TR1/CXX11 checks into separate CMake file

Change-Id: I8f7c4278b8a0a55e8fff8825e0ee4f9801dcc3de
ENH: rename static_assert cmake variable, move test to common cxx file

Rename SITK_SUPPORTS_STATIC_ASSERT to SITK_HAS_CXX11_STATIC_ASSERT for
common CXX11 tests. Move compile test to common file for CXX11 features.

Change-Id: I28644bc5c259f5cbce5ae730378767e7940b6184
ENH: refactor cxx11/tr1 feature detection, features in util namespace

The detection of TR1 and CXX11 features has been refactored into a
separate cmake file, with more uniform names. The compile tests are
now in a single sitk_check_cxx11.cxx files, and tested with custom
macro. More then just a header tests is now down to verify basic
functionality. Additionally, there is a single check for tr1 headers
in tr1 include path. And tr1 features are more then header test which
now distinguishes between tr1 and cxx11 interfaces.

The CMake and configuration variables are now renames to uniformly
describe TR1 and CXX11 features.

To provide a uniform interface the tr1 or cxx11, which reside in
std::tr1 and std namespaces respectfully, classes are now "used" in
namespace "itk::simple::util".

Change-Id: Id23cc87227b5a2f5d32f102a8b46d86315bf26c9
Renames util namespace to nsstd

nsstd - non-standards standard template library.

Change-Id: Ia0a75b32b851271211394413c80af874e81a9faa
Rename util to nsstd in install directory source path

Change-Id: I863781fae9ee891d85bf24413746da0c5c2c1688
Merge topic 'SIMPLEITK-453_EnableCXX11WithoutTR1'

dc679e69 Rename util to nsstd in install directory source path
e844b2c1 Renames util namespace to nsstd
c815acfd ENH: refactor cxx11/tr1 feature detection, features in util namespace
48166aa5 ENH: rename static_assert cmake variable, move test to common cxx file
d4505c51 Separate TR1/CXX11 checks into separate CMake file