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)

examples/http/README.md

@@ -0,0 +1,15 @@
+# GDPM HTTP Example
+
+This is an example showing how to use the GDPM HTTP library to download files. The library uses RapidJSON to get results.
+
+
+Here is a quick snippet to get started:
+```c++
+// Get a full list of assets
+rest_api::context context = rest_api::make_context();
+rapidjson::Document doc = http::get_asset_list(
+	"https://godotengine.org/asset-library/api",
+	context
+)
+// ... parse the rapidjson::Document
+```

examples/http/main.cpp

@@ -0,0 +1,9 @@
+/*! Example using the `libgdpm-http` library
+*/
+
+#include "http.hpp"
+
+
+int main(int argc, char **argv){
+	return 0;
+}