Task/script refactor (#446)

* scripting working with race conditions

* new service works with no race conditions

* use new scripting service and commented out tests

* refactored peek definition to use mssql-scripter

* fixed peek definition tests

* removed auto gen comment

* fixed peek definition highlighting bug

* made scripting async and fixed event handlers

* fixed tests (without cancel and plan notifs)

* removed dead code

* added nuget package

* CR comments + select script service implementation

* minor fixes and added test

* CR comments and script select

* added unit tests

* code review comments and cleanup

src/Microsoft.SqlTools.ServiceLayer/Scripting/Contracts/ScriptingOptions.cs

@@ -101,6 +101,7 @@ namespace Microsoft.SqlTools.ServiceLayer.Scripting.Contracts
         ///   ScriptCreate
         ///   ScriptDrop
         ///   ScriptCreateDrop
+        ///   ScriptSelect
         /// </summary>
         /// <remarks>
         /// The default is ScriptCreate.