inspector: Split out a function
inspector: Add type column to statistics

Rename old type column to "type name"
inspector: increase type by right amount

It's a shift, so we better shift it!
inspector: Update all statistics in same place
inspector: Make all statistics columns visible always
inspector: Kepp tree iter in type data

This way we don't have to clear/refill the model every time but can keep
the existing model and only update the values.

A nice side benefit is that running an update keeps the current selection.
inspector: Add a GraphData object for recording data

This way we can keep more data than just the 2 last values.
inspector: Add a graph cell renderer

... and use it to display graphs for how object counts changed.
inspector: Replace reload with record

and when pressed, record instance counts at 1fps.
inspector: Add missing files
tests: Make gtkgears compile without complaints