Fixed bug with windows not saving properly. (Issue #86)

Frame now correctly removes itself from the client window list when it
is automatically closed for having no open tabs. (Issue #86)
Fixed bug with add tab icon disappearing with multiple windows. (Issue
#85)

Each tabbed pane now has its own add tab icon so it does not disappear
when additional tabbed panes are created. (Issue #85)

The deactivated add tab pane is no longer selected when moving a tab out
of the tabbed pane.

Frame titles now correctly fill gaps in the iteration.