Add option to show total transaction volume since visiting the site

Add a counter that counts up with each transaction, so that you can tell how many bitcoins have been sent since you opened the web page.

Start by locating the code that receives and displays each Bitcoin transaction on the web page. Trace where transaction values are handled, then identify the existing display area for a counter. Done means the total increases for each transaction and starts over when the page is opened.

Written by the indexing model from the issue text.