Remove unneeded code from mainwindow.

This setup is now performed by GLWidget when the tool is added to it.

Change-Id: I6dd2a80038f75fdd113b172fade989c0b6db1c3e
Use the navigate tool by default, or edit if the molecule is empty.

Change-Id: I5406d7e9fa4123686d11627a914a383f35e9e697
Merge topic 'glwidget-tools' into master

eaa0c7d5 Use the navigate tool by default, or edit if the molecule is empty.
fa3a6f39 Remove unneeded code from mainwindow.