Add ability to find countries by alias in country select fields

[timcowlishaw]

Eg 'UAE' vs 'United Arab Emirates', 'Spain' vs 'España', etc. Ideally eventually this should include any widely recognised abbreviations as well as the name of the country in its native language(s), as well as in the currently selected UI language, but we can prioritise the countries where we have an existing user base for now (and make additional aliases configurable in the admin)

From @MansiBavishiUAE on #92:

Currently only if i type Unite arab emirates does the country show up. I should be able to type UAE and still the country should show up.