Fix layout manager default minimize behaviour

[afonsobspinto]

The default minimize behavior doesn't seem to work due to:

• getActiveNode is undefined

It also seems to be enforcing the minimize panel to be at the bottom border, ideally applications would be able to customize this.
The cause of the above problem seems to be that the name of the widget in the widget map doesn't seem to take the 'name' attribute but rather 'type'-'location'