Revert "CSS: Removed drag 'n drop handlers"

This reverts commit 00b672e758709068449344bf0a2e52a431ad8369.
Removed drop handlers without breaking the build
CSS: Browser Link Intellisense for media queries
JS: Added Intellisense for Object.observe
CSS: Removed 2 features that will ship in Update 3

1. Animation name Intellisense
2. Imported font family Intellisense
Compiler: Fixes sourcemap regex. (#1123)
Bundling: fix problem with new bundles
Merge pull request #1131 from am11/master

Compiler: Fixes sourcemap regex. (#1123)
Merge pull request #1126 from GProulx/FixBundlingJS

Bundling: Fix for new bundle