Improve localizer taglib to accept available locales

Hey Eduardo,

I'm working on story LPS-37886 that allows user to define available locales and default locale per site. So you can have Site A in Spanish and English (Spanish by default) and Site B in Portuguese and French (Portuguese by default)

Then, I need to extend the localizer taglib to accept available locales, because right now it's hardcoded and it's getting all the available locales of the portal.

I have sent the first commit to Brian (https://github.com/brianchandotcom/liferay-portal/pull/12579).

Nevertheless, that's only the first part, because the localizer also has some javascript code that I didn't modify in Brian's pull. 

So, I need to do the same in the javascript part: modify the input_localized.js so it accepts the availableLocales as a parameter in the component because right now it seems that it's not possible.

@jbalsas suggested the solution I'm sending to you so you can review it and let us know if it's good or if there is any other approach we should follow.

Thanks!

cc/ @JorgeFerrer