Support language-dependent resources for custom rule sets

[ghost]

The format supports language-dependent resource lookup for a tool. But if the tool accepts plug-in rule sets, and they have language-dependent resources, there's nothing in the format to locate them.

This might not be a problem if the plug-ins have their own resource probing logic, for instance:

CodeScanner\
    CodeScanner.exe
    PlugIns\
        SecurityRules\
          SecurityRules.dll
          en-US\
          fr-FR\
        AccessibilityRules\
          AccessibilityRules.dll
          en-US\
          fr-FR\

[michaelcfanning]

Closing in preference of #179, which is a general tracking issue to consider this issue in an exhaustive way. That analysis may or may not lead to filing specific design issues to address.