DangerousMemberUsagesAnalyzer should be available for other types

[mthjones]

In various places in the LMS codebase, we (ab)use the Obsolete attribute to mark methods as being unsafe for general consumption, leading to inaccurate obsoletion warnings being reported. The dangerous members usage analyzer seems like an appropriate alternative, except that there is no way to mark a type as being dangerous without baking it into the analyzer.

To support this, a new attribute could be added to be able to mark members as dangerous (e.g. [DangerousMember( "foo bar baz" )]). Users of the method would need to either be marked [DangerousMember] themselves or be marked with either the Audited or Unaudited attributes that are already being checked for.