Add 'i18nMetadata' and 'lang' properties to Interactive JSON

[#69671508]
Add flag images

[#69671508]

Generated using:
https://github.com/koppi/iso-country-flags-svg-collection
(MIT License)

PNGs look better than SVG when scaled to small size.
Add language select menu

[#69671508]
Add locales metadata and Polish translation of "Oil and Water"

[#69671508]
Do not setup language select menu when i18nMetadata isn't available

[#69671508]
Serialize 'lang' and 'i18nMetadata' properties

[#69671508]
Add missing CSS styles of the language icon

[#69671508]
Add Spanish translation of "Oil and Water" and update Polish one

[#69671508]
Add i18next submodule

[#69671536]
Use dash instead of underscore for language codes like "en-US"

[#69671536]

It just looks better in menu and fits convention that is used by
i18next.
Support i18n of the main links and tooltips, add Polish translation

[#69671536]
Add i18next to RequireJS config used by tests

[#69671536]
Support i18n of the About, Share and Credits dialogs, add Polish translation

[#69671536]

TODO:
Copyrights, part of the Credtis dialog (visible when
Lab.config.sharing == false).
Support translation of copyright text, add Polish translation

[#69671536]
Support translation of credits dialog when sharing == false

[#69671536]

+ add Polish translation.
Add "interactiveRequested" event to Interactives Controller

[#69671508]

Implement it's handler and use it in language select menu to load
translated interactive.
Support translation of amino acids context menu, add Polish translation

[#71130650]
Support translation of mutations context menu, add Polish translation

[#71130650]
Add Polish translation of Sensor interactive

[#71130650]
Support basic translation of sensor model, add Polish translation

[#71130650]

Missing:
- sensor measurement names
- messages