Create language and currency selection

[jasiek-net]

As an user I want to pick up from app bar menu language and currency.

• [x] add buttons Language to menu
• [x] add nested menu with language pl/en
• [x] save user settings in local storage (and load them back)

[michalmikolajczyk]

@jonzee please do not add a settings button

[michalmikolajczyk]

as a user,
I want to be able to set the language of the app,
on every view, directly from the app bar

as a user,
I want to be able to set the currency,
on every view, directly from the app bar

[jasiek-net]

I created pull request #176 with language selection, now I want to discuss the currency selection. For now currency is strictly connected with translations (so I have to rewrite some parts of code) and I would create a new pr with this feature. I'm not sure where to add currency button. In desktop there are 5 buttons in menu, and I'm not sure if another long button (Currency (USD)) would be fine. I tried to use some icons (like world_icon (PL)) but it wasn't ok. @michalmikolajczyk, @lam3lka what do you think?

[michalmikolajczyk]

Chodziło mi o string z kodem języka "PL" gdzieś w app bar, np. Jako drugi element od prawej. Lub trzeci od prawej, bo drugim powinna być waluta. Można dać tak: <ikona> <string> <flag> PL | <coins> PLN Flaga ikonka ogólna, nie Polski

[jasiek-net]

ok, added to #176

[michalmikolajczyk]

ok.

• [x] select box otwierany w dół
• [x] wersja z ikonkami

[michalmikolajczyk]

[jasiek-net]

added in #176

[michalmikolajczyk]

good work