Created by: hustliyilin

1. sink the implementation of PAL V2 APIs: Move the implementation of skeleton PAL V2 APIs from liberpal-skeleton-v2.c to liberpal-skeleton.c
2. ignore *.so, *.token and Dockerfile.
3. add sanity check in skeleton PAL APIs.
4. support the debug arg.
5. support PAL API V3: support pal_get_local_report API and remote attestation at bootstrap, add skeleton_remote_attestation_with_rune.md.

Signed-off-by: Yilin Li YiLin.Li@linux.alibaba.com