Revert "Changed VS version to MSVC version and added support for VS 2013 and TDM compilers."

This reverts commit 004c12cfd2e4076d6ac5c8105948fa052e4a4406.
Revert "Made compiler and OS variable names much clearer in CMake files"

This reverts commit 9b0ed300b5ced8f9bd49be42089b2988c4007947.

Conflicts:
	cmake/Config.cmake
Revert "Changed the default value of SFML_INSTALL_PKGCONFIG_FILES to FALSE (the generated pkg-config files contain local paths and thus are not suitable for distribution)"

This reverts commit 93b2152a08f0efc8488fda0c0abfe72834bf79c0.