More refactoring and bug fixes

- Added `libhttp` and `librest_api` targets to CMakeLists.txt
- Added examples for `libhttp` and `librest_api` in examples directory
- Added `cache` and `add` commands
- Added documentation for `libhttp` and `librest_api`
- Added all available HTTP response codes to REST API
- Changed how `bin/compile.sh` works (must supply args to build)

include/concepts.hpp

@@ -0,0 +1,6 @@
+#pragma once
+#include <string>
+
+namespace gdpm::concepts{
+	template <typename...Args> concept RequireMinArgs = requires (std::size_t min){ sizeof...(Args) > min; };
+}