Added bip and private key utilities

[edtubbs]

Exposes bip32, bip44 and private key encoding utilities.

[xanimo]

ACK, tested on x86_64-pc-linux-gnu.

[michilumin]

OK to merge just TODO: later want to change this so it doesn't require a pointer and memory address reference because it cuts off accessibility to some other languages; want to retool it so that a chainparam is selected via an option/integer/value, not feeding it the chainparams pointer.

[michilumin]

TODO: want libdogecoin api to eventually never require pointers, so should replace pointer addr input with parameter.

[michilumin]

TODO: same here with pointer intake, should require main/regtest/testnet as option for chainparams not the actual chainparams structure address

[edtubbs]

Agreed, I'll work to wrap the functions with pointers so that they're not necessary.

[michilumin]

Approving but with the caveat of later rework on needing to manipulate/send a pointer addr to use.