Implement Inclavare Containers PAL interface in WAMR Linux-SGX (#429)

* Implement the PAL interface for rune

Work in progress

Signed-off-by: Le Yao <le.yao@intel.com>

* Support PAL for one runtime with multi-instances

Load runtime into enclave and run multi-instances

Signed-off-by: Le Yao <le.yao@intel.com>

product-mini/platforms/linux-sgx/enclave-sample/App/wamr-bundle.md

@@ -0,0 +1,65 @@
+# Run WAMR bundle for Rune
+
+## Create WAMR Application bundle
+
+In order to use `rune` you must have your container image in the format of an OCI bundle. If you have Docker installed you can use its `export` method to acquire a root filesystem from an existing WAMR application container image.
+
+```shell
+# create the top most bundle directory
+mkdir -p "$HOME/rune_workdir"
+cd "$HOME/rune_workdir"
+mkdir rune-container
+cd rune-container
+
+# create the rootfs directory
+mkdir rootfs
+
+# export wamr application image via Docker into the rootfs directory
+docker export $(docker create ${wamr_application_image}) | sudo tar -C rootfs -xvf -
+```
+
+After a root filesystem is populated you just generate a spec in the format of a config.json file inside your bundle. `rune` provides a spec command which is similar to `runc` to generate a template file that you are then able to edit.
+
+```shell
+rune spec
+```
+
+To find features and documentation for fields in the spec please refer to the [specs](https://github.com/opencontainers/runtime-spec) repository.
+
+In order to run the target applications in WAMR with `rune`, you need to change the entrypoint from `sh` to `/run/rune/${wasm_app1.wasm}`, and in order to run multi-applications in one runtime with enclave, change it to `/run/rune/${wasm_app1.aot}`, `/run/rune/${wasm_app2.aot}` ... 
+
+```yaml
+  "process": {
+      "args": [
+          "/run/rune/demo.aot"
+      ],
+  }
+```
+
+and then configure enclave runtime as following:
+
+```yaml
+  "annotations": {
+      "enclave.type": "intelSgx",
+      "enclave.runtime.path": "/usr/lib/libwamr-pal.so",
+      "enclave.runtime.args": "./"
+  }
+```
+
+where:
+
+- @enclave.type: specify the type of enclave hardware to use, such as `intelSgx`.
+- @enclave.runtime.path: specify the path to enclave runtime to launch. For an WAMR application, you need to specify the path to `libwamr-pal.so`.
+- @enclave.runtime.args: specify the specific arguments to enclave runtime, separated by the comma.
+
+---
+
+## Run WAMR Application
+
+Assuming you have an OCI bundle from the previous step you can execute the container in this way.
+
+```shell
+cd "$HOME/rune_workdir/rune-container"
+sudo rune run ${wamr_application_container_name}
+```
+