The attached patch adds support for parsing the application version value from a program-source file. Here is modified documentation for "installation-files.html":
<appversion> : the application version. The version value may be specified directly, or it can be parsed from an application source file via the following attributes:
specSourceFile : path and name of file to be parsed.
specMatchString : match string of characters before version value.
After the match string, spaces, an equals sign, and surrounding double-quotes will be removed (if found). Example usage:
specMatchString="public final static String IZPACK_VERSION"/>