Allow application rules to control window size (Fix bug 4661)

Allow application rules to control window size (Fix bug 4661)

Use the following in your per-app rules:

<size>
  <width>A</width>
  <height>B</height>
</size>

A and B can be integer values to specify a size in pixels. They can also be
percentages or fractions to be relative to the size of the monitor the window
is placed on.