removed CI v2.1.0 system files.
dropped in CI v.2.1.3 system files.
synced mimetypes config with CI v2.1.3 distro
added "core" and "third_party" directories to application folder
added index and .htaccess files to cache directory and whitelisted them in .gitignore file.
added index file to cache directory and whitelisted it in .gitignore file