addressed some feedback on IsInvalid and some other decision we made …

Add IOperation support for tuple expressions

* Change the IOperation unit test dump format for child nodes

* fixing the newly merged tests.

IsInvalid -> HasDiagnostics
removed HasChildren interface and merged it to IOperation

Merge master to features/ioperation

Remove redundant OperationKinds

Disable failing CSharpSendToInteractive Tests

Better respect lang version when generating expression bodies.

Fix a possible null ref in SymbolTreeInfo.

Merge master to features/ioperation

Merge master to features/ioperation

Fixed InlineTemporary into a invocation of local function 

Perform the initial tagging for a file as fast as possible so that that the file appears 'complete' immediately after opening.

Remove parts of pattern matching that are no longer needed.

This PR adds the initial work for a new closure conversion design based around a tree instead of a series of dictionaries. The tree should

Make it easier to assert invariants as we perform rewriting.
Make debugging simpler.
Allow us to move to a series of cheap, simple passes over the simplified tree, rather than one, very complicated pass over the bound tree.
Make it easier to move almost all logic into the analysis phase and make rewriting a simple mechanical transformation.
The heart of the new design is the Scope tree, which consists of a series of nested Scopes, each of which hold relevant information about what variables and closures are declared in that scope. The Closure, meanwhile, holds information for each closure, including a list of captured variables. By carefully visiting the bound node once we should be able to encode all relevant information into the Scope tree, and then iterate over a series of quick, simple passes to create the fully converted form.

Infer better types for values to ref/out arguments.