Couple of small updates to rfid.esp and add more comments

[mcnewton]

• No need to test (uid.length() == 0) multiple times in genericRead, put all the alternative hardware in one 'if' block.
• Quote the debug 'Username' to make it easier to read
• Add more comments to help people like me understand what's happening :)

[matjack1]

@mcnewton looks like this is not changing anything right? It's fine if you want to add comments, just make it clear if you want to change code while you add comments so that it's easier to review.

If you want to get this merged, can you please resolve the conflict? Thanks!

[mcnewton]

Hi @matjack1 - it's mainly comments, yes - but there's a small tidy lines 175-187 where it pulls the && uid.length() == 0 off three if statements and just wraps them all in if (uid.length() == 0). With optimisations it probably compiles down to the same thing, but makes it a bit easier to read. I did mention it in the PR comment.

I'll rebase and update the PR - I made the PRs so they could be pulled in independently, but figured that if you tried to pull them all in they might clash slightly :) Thanks for pulling the rest of them!

[matjack1]

Cool, thanks :)