have createblindedaddress use blinding pubkey instead

[instagibbs]

@Christewart we found this to be more useful downstream, so we switched.

[Christewart]

Just tried this, doesn't seem to work they way I was talking about in #124

Here is the paste bin of what I was trying: https://pastebin.com/CwirDfew

[instagibbs]

@Christewart I replaced that error message, it should say "Invalid hexadecimal key length, must be length 66." instead if the length is wrong?

[jtimon]

@instagibbs Can you confirm that this needs rebase to 0.14 ?