Use SwiftGen for strings

[Kharchevskyi]

What do you think about using SwiftGen in the project?
This tool will automatically generate swfit type safe code for strings.

https://github.com/SwiftGen/SwiftGen

* Avoid any risk of typo when using a String
* Free auto-completion
* Avoid the risk of using a non-existing asset name
* All this will be ensured by the compiler and thus avoid the risk of crashing at runtime.

Besides that it would be easier during code review to make sure all strings are localized.
@sosnovsky

Originally posted by @Kharchevskyi in #956 (comment)