[botservice] Prod. environment is polluted with dev. dependencies.

### Extension name (the extension in question)
botservice or any extension that installs node dependencies.

### Description of issue (in as much detail as possible)

devDependecies should NOT be installed when running `npm install` in production environment.

[Found here](https://github.com/Azure/azure-cli-extensions/blob/master/src/botservice/azext_bot/custom.py)

[Solution](https://docs.npmjs.com/cli/install) `npm install --production`.

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