Add InitError(error, details) overload

This is only used in the current PR to avoid ugly
`strprintf(Untranslated("%s:\n%s"), str, MakeUnorderedList(details)`
boilerplate in init code. But in the future the function could be extended and
more widely used to include more details in GUI error messages or display them
in a more readable way, see code comment.

src/shutdown.cpp

@@ -27,7 +27,7 @@ bool AbortNode(const std::string& strMessage, bilingual_str user_message)
     if (user_message.empty()) {
         user_message = _("A fatal internal error occurred, see debug.log for details");
     }
-    AbortError(user_message);
+    InitError(user_message);
     StartShutdown();
     return false;
 }