Fix the text wrapping in the rendering progress dialog

The trick is to:
- Make the window resizeable and set a default width for it
- Set the "width_chars" property on the label

Fixes bug #728218
Bump the GStreamer dependency to 1.4
Make the "User Manual" menu item work in the main MenuButton

This item was insensitive because it was bound to the wrong action name
Make the title editor's infobar more compact to avoid excessive wrapping
For non-toolbar dialog buttons with labels, remove superfluous icons

The recent slew of changes in master added extra icons to various buttons.

In 2011 I would not have imagined that I'd be in favor of this in 2014,
but I've gotten used to not having random icons on buttons anymore.
It's also easier to support as an app maintainer, with more labeling freedom.

This commit also clarifies some button labels, replacing "Clear" by "Reset all".
Fix the width of widgets in the "Info" tab of the Project Settings dialog