CMake-related work

• Adding cmake's conan.io support + appveyor's support for conan.io
• Adding shared library versioning
• Adding back cmake 2.8 support (from previously required 3.0 version) (Thanks to @bbczeuz/Claudius Zingerli)
• Using CMake’s GnuInstallDirs for better install rules on unixes platforms
• Making shared and static libraries have the same root name, but different suffixes.
• Applied GnuInstallDirs change from Ximin Luo infinity0@debian.org
• CMake RPATH Handling: In response to CMake 3.0 generating warnings regarding policy CMP0042, the OSX RPATH settings have been updated per recommendations found in the CMake Wiki:
  • https://www.cmake.org/Wiki/CMake_RPATH_handling#Mac_OS_X_and_the_RPATH
  • https://blog.kitware.com/upcoming-in-cmake-2-8-12-osx-rpath-support/