simpleststore and local pages fixes

[miki-totefu]

No description provided.

[karamble]

Ok. The addToCart works now for a user that uses /pages local
You can change quantities and add products to your cart.
When placing your order you receive a lnpay:// invoice

Further Suggestions:

Make the /ln payinvoice command understand the lnpay:// prefix when copy pasting it to pay the invoice.

The output message when placing an order looks good!
It has a list of ordered items, price in USD, the total amount and the exchange rate for the total sum of expected DCR to pay. It mentions the validity of the invoice for 1 hour. This message should be shown in the dialog window of the store, not only in the logfile (/w 0)

If the expected total amount to pay exceeds inbound capacity the [ERR] SSTR: message should also be displayed to the dialog window of the store and not only in the logfile (/w 0). The dialog window in the store shows "order completed!" instead, which is misleading.

[miki-totefu]

did the first 2 things

the last one is useless, because the user can't do anything about the store having no inbound capacity. i changed it to generate an onchain addr when generating the ln invoice fails