For each package, show a tree of the downstream dependent packages

For each package, show a tree of the upstream dependent packages. (dependencies are shown, but not its downstream dependents).

As an example, I didn't explicitly install 'Gow' and would like to look at which programs required it because I am having problems with gow's vim.exe taking precedence over the vim.bat that comes with the vim package. Of course, this problem with gow isn't related to ChocolateyGUI. But having a feature to let me query what other packages are using a package would help debug problems like this.

As an implementation example: See npm's packages. On https://npmjs.org/package/bower it shows dependencies and dependents.

Start by locating the existing package dependency display and the data source used by ChocolateyGUI, then compare the requested downstream view with npm’s dependencies and dependents example. Done means a package can display its downstream dependent packages as a tree, including the use case described for Gow.

Written by the indexing model from the issue text.