Double down or remove use of empoweredBy in invoice template

The invoice template but exactly ZERO of the other templates adds the empoweredBy CiviCRM logo to the header.

As part of trying to consolidate template handling code I want to EITHER

• switch to using a token for the empoweredBy image OR
• remove it from the invoice template (on new installs- but in the long-term it might break on existing ones if I do that)

I feel an emoji poll coming on - go on - be Caesar - thumbs up it lives - thumbs down it dies (although death would be slow & gradual in this case)

Tangential issues

• invoice also uses an image-based horizonal line - I'm leaning towards making that a token {formatting.line} but that is for a separate issue
• this brings up a bunch of feature requests around what WOULD be useful in place of the empoweredBy. I did chat with Tim on that & will try to put it in another issue