When reading config from a file, Simulator should emulate all devices specified times device count.

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### This issue is for a: (mark with an `x`)
```
- [ ] bug report -> please search issues before submitting
- [ ] feature request
- [x] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)
```

### Minimal steps to reproduce
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### Any log messages given by the failure
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### Expected/desired behavior
> When reading the configuration from a file, the Iot Telemetry Simulator should emulate all devices specified times the device count defined in the env vars (Default=1).

### OS and Version?
> Windows 7, 8 or 10. Linux (which distribution). macOS (Yosemite? El Capitan? Sierra?)

### Versions
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### Mention any other details that might be useful

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