Wireleap integration using Zeekoe

[gijsvl]

Change the Wireleap integration proof of concept that uses the PoC cli to use Zeekoe.

Changes needed:

• Change in Wireleap repo: examples/ps-zkchannels Call Zeekoe Merchant instead of CLI Merchant.
• Change in wireleap-cli that is inside libzkchannels-blindsigs: Use Zeekoe Customer instead of CLI Customer.
• Make sure the purchases is properly associated with the payment.