CMake isn't configured to search for all dependencies

CMake is designed to allow a search for project dependencies on the system before compilation and display an error message if the dependencies don't exist. When the dependencies are found the library and include paths can be added to the build. At the moment we are only searching for the boost library, however we now have dependencies on OpenAL and ASIO and in future we will have a dependency on SDL 1.3. We need to fix up the cmake files to search for these libraries, add the correct include and library paths. If the dependency is found a link to the associated website should be displayed in the error message.