Implemented application language change behavior and setting

[sgourdas]

I have added logic to implement language change from the settings menu with a dropdown menu trying to close #478

[kelson42]

@sgourdas Here again sorry for the lack of feedback, this is a bit more PR than usual :) Can you please rebase it on main and fix the conflicts?

[kelson42]

This PR works "in principle" but suffers from many problems:

• The user is not invited to restart the app after setting a new language in the settings
• The languages in the select box are all in English. Either it should be in the language of the current UI OR each language should be written in its own language
• Many language are just "C"
  

[sgourdas]

I have refactored the logic to dynamically import language codes from the available files in the i18n folder. The following issues have been observed:

• io.json and nb.json do not have a name field, necessary for getting the native name of the language. Regardless I have a check in place to skip files with this issue, but I think we might need to make sure that only substantially complete languages are in this directory, to be used.
• A lot of languages are incomplete like yo.json or bcl.json where even the name field of the json file is incorrect and misleading. One check I have in place to mitigate these issues is if QLocale(code).language() returns C I skip this language.
• Languages like Chinese are unable to be rendered with our font and I am not sure how to proceed with this.
  
  Some examples are বাংলা" (bn.json), हिन्दी (hi.json), 英語 (ja.json), 한국어 (ko.json). If you want the complete list please ask me.