[worksheet] changed the default fit behavior from None to Fit

Description

Changed the default fit behavior from None to Fit to better use the available space.

Before this change our standard worksheet+plot looked like:

After the change:

So, the worksheet still has it's initial size 10cm x 10cm, but we zoom to fit the available free space. This behavior is similar to other applications that also zoom the "document" on start to better use the available space.

The user still can switch to "None" in the fit menu in the toolbar, if needed.

Conformity

• Changelog entry
• Unit tests
• Update INSTALL
• Downport
• Fixes:

When external dependencies are removed

• Reporting to ...