Rename RPC `getfundingaddress` to `getpeginaddress` for clarity
Rename RPC `getfundingaddress` to `getpeginaddress` for clarity

Improve the help text to better explain what the command does, and how
`getfundingaddress` parallels `getaddress` in necessitating regular backup
of wallet.dat.

kallewoof/elements,tdudz/elements,tdudz/elements,tdudz/elements,kallewoof/elements,tdudz/elements,tdudz/elements,kallewoof/elements,kallewoof/elements,tdudz/elements,kallewoof/elements,kallewoof/elements