Feature request: support non-ui plugin types

[alexziskind1]

While the structure that the plugin seed creates is very handy for plugins that are destined to add some functionality with native libraries, there is no clear path to enhance existing functionality.
For example, let's say I wanted to add a new method to the EXISTING View class, I need a plugin that creates the new method, appends the new method to the existing structure, and adds the necessary typescript definitions.
If I wanted to add a fadeIn method to the existing View class, I need to add this typescript definition:

import { View } from 'tns-core-modules/ui/core/view';

declare module 'tns-core-modules/ui/core/view' {
  interface View {
    fadeIn(duration?: string | number): Promise<void>;
}
}
...

Then I need to add the extra method to the existing View prototype.

import * as viewModule from 'tns-core-modules/ui/core/view';

viewModule.View.prototype.fadeIn = function(duration) {
...
}

So in this case I also don't need the extra platforms/android and platforms/ios folders or the files within.

This is one example of a plugin and would be great if it's supported.