add option to hide country flag on header

[hugosolar]

Fixes #24

Description
Option added to the Dashboard > custom settings screen to hide the country flag in header

Checklist:

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the master branch of the repository.
• My commit messages follow best practices.
• I added tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no
  visible errors.

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