1.5.0

• update to 2021 rust edition
• use async_channel to replace the rust native channel.
• plugins directory can be configured in .env file, the property is PLUGIN_PATH, or you can put them under the work directory .
• use Local-Time for logger
• move NatureError and Result to common module。
• includes all executable files and executors which demo need in release package
• doc repair
  • Readme.md
  • doc/ZH/help/executor.md
  • nature-demo/doc/ZH/prepare.md
• remove the support for sqlite.
• demo for multi-warehouse: fix data duplicate problem.