Gather possible widgets

[haassie]

As a product owner I want to know what kind of widgets the users would like to have so I can decide which widgets we will ship in the first release. It is important that the information it gives, is available from core-extensions. We will not ship widgets for third party extension. However, we will actively help extension developers to add their own widgets to their extensions.

This is an ongoing task, but this is issue is now only ment for the first release.