995c797e0d feat: generate PrivateKey (kshitjj)
Pull request description:
added a function to generate a private key
Resolves: #1823
ACKs for top commit:
apoelstra:
ACK 995c797e0d
tcharding:
ACK 995c797e0d
Tree-SHA512: 29ba54be8cb777e71a4683835686cbf2978b23736f629d7bbff468074235fece261ca170c23f358d1bd878987566d09e4488c3f1a106c59a5c8bdf52b98abffe