Feature request: Add capability to remove components

Currently the CLI provides us with the capability to generate components using the **generate** command. Assume that we need to generate a page, we use the `ionic generate page games-list`. This will generate a directory which contains a .html, .ts and .scss file for us and add an entry within the _declarations_ and _entryComponents_ array in the app's root module: _app.module.ts_.

Now for some reason if we want to delete the _games-list_ component we will have to manually delete the folder and remove the entries in the _app.module.ts_. In many situations the developer may forget to do the second step i.e. to remove the entries from _app.module.ts_ which results in an error.
PS: I have faced this error many times in the initial stages of development. I keep forgetting to remove the entries.

In order to avoid this error, we can introduce **remove** command which removes the component folder as well the entries from the app's root module.
`ionic remove page games-list`

Start by tracing the CLI's existing generate command and how it updates app.module.ts. Define the remove command for a generated page such as games-list, covering both its directory and the declarations and entryComponents entries, then verify the resulting module remains valid.

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