Add graphical language configuration option

[Master92]

This PR re-applies changes by @ligenxxxx i.e. it adds a drop-down configuration box of the current UI language in the firmware page. I tried to localize as much as possible but need some help translating the strings in lines 250 and 251 of the ini files to Russian and Chinese. Maybe @Sat1l and @ligenxxxx might want to help me out there?

Another thing I added was automatical removal of the text file used to configure the UI language once it has been applied. This way, you can still initially configure the language from an SD card file while also being able to change it in the application afterwards.

English

Chinese

Russian

[lesharodin]

@Master92
Here is some fixes of translation:

I think you need to leave this in English, because there is no need to translate that, and when you change settings on VTX it will say you in English to change Bandwith of googles to Wide or Narrow, and with translation it could be confusing

HDZero BW = "HDZero BW"
Wide = "Wide"
Narrow = "Narrow"

Some fixes:

Use VLC Player to open a Network Stream = "Используйте VLC Player для просмотра трансляции"
Set Alarm Angle = "Установить угол предупреждения"
Pan = "Поворот"
Tilt = "Наклон"
Roll = "Крен"
To view release notes = "Для просмотра изменений"
then press the Func button to display or hide the release notes = "Потом нажмите кнопку Func для отображения или скрытия изменений"
Release Notes = "Список изменений"
Focus Chart = "Фокусировка"
Go Sleep = "Режим сна"
Go Sleep! = "Режим сна!"

[Master92]

@lesharodin Thanks for your input. However, I'd not include them in this PR because they don't directly relate to my changes. You could open a new PR with those fixes so they can be discussed and applied separately.