Refactored the _Layout page using Microsoft ASP.NET Web Optimization Framework

- Introduced a new dependency on `System.Web.Optmization`
- Centralized all bundling logic in `BundleConfig.RegisterBundles()`
- Bundled all JS and CSS for faster page loads (turn debug mode off to see the effects)
- Converted to HTML5 Doctype

However VS2013 has slightly modified the `.csproj` file for debugging purpose. May have to resolve conflicts on that.