Synced redundant base qualifier issue/improved redundant this
qualifier issue.
Synced 'EmptyNamespaceIssue'.
Synced 'EmptyDestructorIssue' / improved EmptyConstructorIssue.
Synced 'CS0759RedundantPartialMethodIssue' - in fact this issue is a
semantic compiler error.
Changed API of GatherVisitor to encourage giving meaningful
descriptions for the code issue tooltips and issue actions.
Improved many descriptions / categorized some code issues.
CS0759RedundantPartialMethodIssue now only marks the method name.
Empty namespace issue is now much less intrusive.
Merge branch 'master', remote-tracking branch 'upstream/master'

Conflicts:
	ICSharpCode.NRefactory.CSharp/ICSharpCode.NRefactory.CSharp.csproj
	ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj