Fix the boolean return of Store::remove()

 - std::map::erase() "For the key-based version, the function returns
   the number of elements erased, which in map containers is at most 1."
Fix the CMake for GCC 4.6

 - GCC 4.4, 4.5 and 4.6 uses the flag "-std=c++0x" instead of "-std=c++11"
 - GCC 4.7 and above can use any two of them

NOTE: this is only part of a fix for building against GCC 4.6 ; I will also provide a fix for the source code
NOTE: GCC 4.6 is used under Ubuntu 12.04 current LTS, and so it is the default for Travis Continuous Integration free services
Fix the CMake for MSVC
Fix CMake of examples for MSVC
Fix msvc build

 - constexpr and custom string literals not supported in VS2013 (only in last CTP preview)
Fix the GCC 4.6 build with a specific patch for the virtual "override" specifier
Merge branch 'fix-msvc-build' of https://github.com/SRombauts/libes into feature-no-cxx11
Merge branch 'fix-gcc-46-build' of https://github.com/SRombauts/libes into feature-no-cxx11
add a COMPILER_IS_NOT_CXX11_READY option
use Support.h and COMPILER_IS_NOT_CXX11_READY
fix examples with COMPILER_IS_NOT_CXX11_READY
add Sébastien Rombauts to the contributors
make includes consistent
Merge branch 'feature-no-cxx11' into develop
Merge branch 'fix-store-remove-return' of https://github.com/SRombauts/libes into develop
update ChangeLog for 0.5.1
replace complicated ifdef with a simpler one
update version number in CPackConfig.cmake
Merge branch 'release-0.5.1' into develop