Do not use the default logo as icon without telling me

# Feature Request

## Motivation Behind Feature
When I start a new blank app, it's convenient to have the Cordova default logo for my app.
BUT when I start to put my own icons and the platform update add some new size (in the xasset), it use the default logo again.
It quite dangerous because I don't know that, and it's very easy to publish an app with these default icons.

## Feature Description
Add a warning on the build phase when using the default logo if there is no custom icon;
Add an error if there is some custom icon, but not all are present.

## Alternatives or Workarounds
For now I have to check manually the xasset filme

Start by tracing the Cordova iOS build phase and the xasset icon handling mentioned in the issue. Determine how the build distinguishes a default logo from a partial custom icon set; done means a warning for the default-only case and an error when custom icons are incomplete.

Written by the indexing model from the issue text.