Setting to change the UI language

[hugomg]

An user mentioned that they would like to use Daily Pill in a language that is different than the system language in the Android settings. This would require adding a way to change the language in the Daily Pill settings screen.

[hugomg]

Eample of FOSS apps that implements this feature:

• https://github.com/j05t/dbclf
• https://github.com/grote/Transportr