FindCppUnit.cmake: Add CPPUNIT_ROOT env var support

With this change it is possible to specify the location of the
cppunit framework.
[CMake] fix cppunit include dir variable (typo)

Actually pick up the correct location set by cmake for the cppunit
framework.
[CMake] only set (gcc/clang) compiler flags on !win32
Platform.hpp: new header for platform specific things

Currently only Win32 specific things are defined here
[win] Value: extract string member from union on win32

VS 2013 has no support for unrestricted unions[1] so we have to
work around it.

[1] http://msdn.microsoft.com/en-us/library/hh567368.aspx
[win32] TestDataSet: VS2013 doesn't like typename in typedef
TestDataTag: Explicitly include <ctime> for time()
[win] TestGroup: Disable 2d array test for now

Cf. issue #72
[win] Export relevant symbol, i.e. add NIXAPI, where needed

Adding NIXAPI will add __declspec(dllexport) when we are
compiling the library itself and __declspec(dllimport) otherwise.
NB: We don't do this for template based classes since linking
is different for them
[CMake] Copy hdf5 dlls to output directory (for tests to run)
[win] Add description how to compile nix on win32

This is the last ingredient to close issue #70
Sync with master

Merge branch 'master' into win32
Conflicts:
	include/nix/Section.hpp
Merge pull request #73 from gicmo/win32

This is awesome
And thanks for the doc in Win32.md