Allow to store configuration in a JDL file.

[mshima]

Add support to store configuration in a JDL file using --jdl-store filename.jdl.

• imports JDL to in memory fs.
• exports JDL from in memory fs.
• a reduced .yo-rc.json with jdlStore, creationTimestamp, jhipsterVersion, jwtSecretKey, and rememberMeKey is written to disk.
• requires a JDL file for each application.
• for incrementalChangelog, entities config files are kept for changes detection.
• annotations are currently not supported by export JDL, entities config files should be kept while annotations are not supported.
• prints an experimental warning.

Fixes #8915.

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