Upgrade to TypeScript 2.6

[kitsonk]

Enhancement

We should upgrade to TypeScript 2.6. The biggest impact is likely to be strictFunctionTypes which will be on by default when using strict.

• [x] dojo/cli
• [x] dojo/cli-build
• [x] dojo/cli-create-app
• [x] dojo/cli-create-widget
• [x] dojo/cli-export-project
• [x] dojo/cli-test-intern
• [x] dojo/core
• [x] dojo/has
• [x] dojo/i18n
• [x] dojo/interfaces
• [x] dojo/interop
• [x] dojo/loader
• [x] dojo/routing
• [x] dojo/shim
• [x] dojo/stores
• [x] dojo/streams
• [x] dojo/widget-core
• [x] dojo/widgets
• [x] dojo/dojo2-package-template
• [x] dojo/grunt-dojo2
• [x] dojo/grunt-dojo2-extras
• [x] dojo/test-extras
• [x] dojo/web-editor
• [x] dojo/webpack-contrib

[bryanforbes]

This was taken care of for grunt-dojo2 in https://github.com/dojo/grunt-dojo2/commit/a033cb496c9a919d28a9e6d03086feafeef35e0c

[agubler]

Removing dgrid and examples from issue and will open specific issues if required.

[agubler]

All packages have been upgraded to TS2.6