Make dynamic endpoint of the gateway class

[sandeepchhawdi]

Hello Team, I just came across the issue where I need to use ae for https://secure.ccavenue.ae/transaction/transaction.do?command=initiateTransaction instead of https://secure.ccavenue.com/transaction/transaction.do?command=initiateTransaction

Need to make protected $liveEndPoint optional to set through config.

Currently I worked to inherit the class and then override the variable. but It took a lot of time to figure out the issue.