Improvements to Customer generator

[coreymckrill]

Changes proposed in this Pull Request:

Makes the data generated by the Customers generator more "coherent" and contextual to a locale, plus a few other enhancements to make it more useful for testing.

• Adds an optional country parameter to the generator, which is used to localize the Faker library that produces the random data. If a country isn't specified, falls back on randomly selecting any country that the store is configured to sell to.
• Ensures that first, last, and/or company name that is generated is then used when generating username and email address.
• Adds an optional type parameter to the generator, to specify if the customer should be a person or a company. Company customers do not have the first and last name fields filled in.
• Sets the password of every created customer account to password so that it's easy to log in as that customer and see the store from that perspective.
• Misc tweaks.

Fixes #131
Fixes #108
Fixes #66

How to test the changes in this Pull Request:

1. Open a tab to your test site's admin and go to WooCommerce > Customers. Sort the table by Date Registered so you can quickly see new customers when they are generated.
2. In your terminal, view the docs for the customers cli command: wp help wc generate customers. Note the optional parameters for the command.
3. In your browser, go to WooCommerce > Settings. Make sure "Selling location(s)" is set to "Sell to all countries".
4. Try the default command: wp wc generate customers. You should get 10 new customers, from a wide variety of countries.
5. Now change the "Selling location(s)" setting to one or two specific countries, and run the command again. All 10 of the generated customers should be from those countries.
6. Try specifying some different countries on the command line, e.g. wp wc generate customers 1 --country=DE and see if the generated data matches. Try some countries that don't use a Latin alphabet, e.g. CN or RU.
7. Try specifying a country code that is invalid.
8. Try choosing just one type of customer, e.g. wp wc generate customers --type=company --country=FR

Changelog entry

Improved test data for the Customers generator.

[naman03malhotra]

Thanks for working on this, it works well 🎉

Two things:

• While testing I observed that cities for some countries are set randomly, as in the city being set is part of some other country, probably that's fine.
• We should do version bump and add changelog as part of this PR.

[coreymckrill]

Thanks @naman03malhotra

While testing I observed that cities for some countries are set randomly, as in the city being set is part of some other country, probably that's fine.

I think this happens when the Faker package doesn't have any city data for that particular locale, so it falls back on the "default" locale, which is en_US.

We should do version bump and add changelog as part of this PR.

Planning to do that, but as a separate PR, because there are several other changes for a new version besides this one!