Add --configDir global flag

[fisuda]

Proposed changes

This PR adds --configDir global flag.

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Update only documentation, not any source code.

Checklist

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• I have read the CONTRIBUTING doc
• I have signed the CLA
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Further comments

N/A

[coveralls]

Coverage remained the same at 100.0% when pulling fa357e3 on fisuda:feature/config_dir into babf9fc on lets-fiware:main.