Listing of all the packages bundled in Visual Studio Ultimate 2015 (on my machine) + few 3rd parties.

Place the file devenv.pkgundef in your C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE (next to devenv.exe), and run devenv /updateconfiguration. The next time Visual Studio starts, it will refresh the pkgdef cache, and will remove all the packages specified in the pkgundef file.

To PREVENT a package from unloading, comment the relevant [$RootKey$\Packages\{...}] line with a semicolon (;).

To undo, delete the devenv.pkgundef file, and run devenv /updateconfiguration again.

USE AT YOUR OWN RISK!