Provide more user preferences

[gmella]

Depending on their most common use case, some user prefer to get Observabilty with Scrollview selected or unseleted.

Providing the default behaviour through a preference could be a very nice way to save number of useless clicks.

Here comes a list of other preferences that may help:

• type of data to underplot as model in the UV Coverage
• ...

[gmella]

Due to lack of time, we will invert the default behaviour for the next public release. This action is postponed and will be generalised to other user preferences.