Help button for many warning messages; Restored warning icon.

The error icon was gone because we are now using the ErrorDialog, which didn't have it.  So added back explicitly.  I decided to go with wxART_WARNING rather than wxART_ERROR because nearly all of these present as warnings.

src/SqliteSampleBlock.cpp

@@ -332,7 +332,9 @@ DBConnection *SqliteSampleBlock::Conn() const
    if (!pConnection) {
       throw SimpleMessageBoxException
       {
-         XO("Failed to open the project's database")
+         XO("Failed to open the project's database"),
+         XO("Warning"),
+         "Error:_Disk_full_or_not_writable"
       };
    }
    return pConnection.get();