DepthFirstAstVisitor no longer tries to visit the children of non C#
ast leaf nodes.
(Speeds up visitors a bit)
CanBeDemotedIssue now respects the
CA1011:ConsiderPassingBaseTypesAsParameters suppression.
Implemented resharper disableing for redundant using directive.
Revert "DepthFirstAstVisitor no longer tries to visit the children of non C#"

This reverts commit 158b5176a2bd0616596a7b2755a18804c7f01477.

The optimization was invalid; the VisitChildren() method is not
necessarily an unnecessary call on leaf nodes because it is virtual.
Add unit test demonstrating that the DepthFirstVisitor optimization was invalid.
Removed debug code.
Implemented array initializer formatting.
[CodeIssue] Redundant Null Check

No need to check null where is keyword exits.