278 configurable headercheck

[Jandev]

Created delegate to let the developers decide what functionality should be implemented when parsing the user request languages. Necessary if you want to skip the "Accept-Language"-header.

This should resolve #278

[turquoiseowl]

Looks very good! Thanks for the contribution.

[Jandev]

Thanks!
Is there an interval you use for creating new Nuget packages, or is it random?

I'm asking so we know when to expect the functionality in a public package.

[turquoiseowl]

I'll push a new package over the weekend.

[jeancroy]

I just wanted to share that history item Support for ignoring Accept-Language request header
Points to this PR. However how to implement said feature is not trivial nor documented.

The problem lie in the fact that said delegate return an array of LanguageItem, a data structure specialized for dealing with Accept-Language request header and the relative scoring of each item.

First I tried to return an empty array. Unfortunately that result in index out of bound exception later.

i18n.HttpContextExtensions.GetRequestUserLanguagesImplementation =
    (context) => new LanguageItem[] {  }; 

Then I tried to return the default language. Unfortunately this involve faking ranks & magic numbers.

i18n.HttpContextExtensions.GetRequestUserLanguagesImplementation = 
  (context) => 
     new[] { new LanguageItem(LocalizedApplication.Current.DefaultLanguageTag, 1.0f, 0) };

This seems better however there's a comment that explicitly warn against using this