Allow BaseAttribute HelpText localization to use internal classes and properties.

[ILMTitan]

Fixes #477.

[moh-hassan]

Thanks @ILMTitan for your effort.

Localization in .NET is based on public (not internal) resources. For example, in DataAnnotation DisplayAttribute, it check for visibility and fire exception for internal resources .

because:

• Resources may move to satellite assemblies, and internal resources are not visible to other assemblies.
• In WPF application, Xaml can't use internal resources.

For these reasons, localization in PR #356 check for visibility and fire exception for internal resources .

I know, in VS IDE by default, resources are internal, but this can be modified easily.

Is there any problems in using public resources?

[ILMTitan]

Moving discussion to issue #477.