The following modifications are done to extract the code that provides the HTML formatting of the messages that appear in the progress panel.

This is done mainly for two reasons:

1. The code in the Installer class should not control the format used (HTML, plain text, etc.) which is more related to the pure UI.
2. Be able to share this formatting code for the graphical installation and also the uninstallation so that we have the same look and feel in both without code duplication.