update HTMLEntitiesCodes.pm with substring replace

HTMLEntitiesCodes.pm
1. Substring replacers
A few practical examples as a result of this change — the following
query pairs will now lookup the same key: ‘trademark symbol’ and
‘trademark’ // ‘up-down arrow’ and ‘up down arrow’ // ‘pound sign’ and
‘pound’, and so on…

2. Update the keys for this change (extraneous keys removed).