App's Podfile should be applied last

[DickSmith]

Environment
Provide version numbers for the following components (information can be retrieved by running tns info in your project folder or by inspecting the package.json of the project):

• CLI: 5.3.1

Describe the bug
The new app Podfile has been immensely useful, however, ideally the App's own podfile should appear last in the generated Podfile. The main reason here is that the App's post_install should be run last, in case Podfiles from plugins perform a similar change.

To Reproduce
Create an App Podfile in App_Resources/iOS, add plugins with Podfiles.

Expected behavior
App Podfile appears at the end.