Fix layer node bugs for list of outputs (STN case) and upgrade model weights property (#956)

[rundiwu]

Checklist

• I've tested that my changes are compatible with the latest version of Tensorflow.
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.

Motivation and Context

1. Fix layer node bugs for list of outputs (STN case reported by @zsdonghao) Core layer todo list for 2.2.X [NEED CONTRIBUTION] #956
2. Upgrade model weights property, now it returns shallow copy Core layer todo list for 2.2.X [NEED CONTRIBUTION] #956

Description

NOTE: Ignore changes in example/database, which is not finished yet.

[zsdonghao]

the docs has error, run yapf -i --recursive tensorlayer should help