A valid package name should be computed as default when prompting for a replacement in a JAVA_PACKAGE prompt

When an invalid package name is supplied as a value for an option whose PromptType is PromptType.JAVA_PACKAGE, then Forge prompt again for a valid value. No default is computed, and thus this is not friendly to scripts or to environments like the JBDS 7 Forge wizards where the shell is not accessible directly.

An enhancement is thus sought to compute a valid default value for such cases.