ColumnManager has to apply the zoom factor to newly added columns. Otherwise,
showing a previously hidden column appears with scale 1.0.
This also drops the value-changed signal emission for the vadjustment, as it is
apparently not needed.
Add two actions to shrink and enlarge the text in the log pane. Add a theme
overide to set expander size to 1 (see bug #615985) and also turn focus lines
off. Remove extra ypadding on cells.
Seems like pygobject can all of the sudden not handle a NULL model on a
property. Using the getter works around this. Also using the setter now for
consistency.
