Try to improve the wording of gender option

* Move the gender option to the internationalisation section,
  because it's mostly used for that.
* Change the displayed values: rather then gender identifiers,
  it demonstrates the usage of the option.
* Update documentation accordingly.

Change-Id: I81f02f03f5992ad5f0501e0a7552bdee9f2c1d5e
Bug: 31816