Add default ToString to SyntaxTree

pushed down GetRelatedDocumentId API down to solution.

Add padding around the lightbulb diff preview

Remove Portable.FX45/project.json, clean up list of global packages

Add EquivalenceKey for suppression code actions to ensure that duplicate equivalent suppression fixes are not shown.

Fixes #3311 

Add *.nuget.targets files to .gitignore

Properly support indentation within text of XML doc comment on ENTER

it should return all related document Ids of given document Id
ex) linked file, project k files, shared project files and etc.

fixes #4803

Flow inference values across generic method return types.

Whitespace after the caret should not be removed When inserting slashes on ENTER in XML doc comments

Move portable TestUtilities and Scripting projects to project.json

Fix C# completion preselection for enums in expression-bodied members

SyntaxGenerator: check for nodes in trivia

Remove constraints for private interface method implementations

Round trip 'Additional Locations' on a DiagnosticData.

Implement Edit.LineOpenAbove and Edit.LineOpenLineBelow commands for XML doc comment generation

fixes issue #4802

Updating Linux/Mac build to use the new toolset.