Make inspector widget a bit smaller by letting the Qt widget system
layout the widgets.
Let the inspector widget calculate its own smallest size. Use stretch
factor of 0 for inspector, 1 for picture canvas.
Group the matrix and clip widgets in groups. Put the text edits in a grid
layout instead of a handwritted column layout containing row layouts.
This commit is part of work that tries to make the debugger window to be
a bit more resizeable, so that it would fit 1900x1200 screen.
Review URL: https://codereview.chromium.org/830743002
7c339ae1e3