* HD wallet
Minimal set of changes (no refactoring) backported from Bitcoin upstream to make HD wallets work in Dash 0.12.1.x+
* minimal bip44 (hardcoded account and change)
* minimal bip39
Additional cmd-line options for new wallet:
-mnemonic
-mnemonicpassphrase
* Do not recreate HD wallet on encryption
Adjusted keypool.py test
* Do not store any private keys for hd wallet besides the master one
Derive all keys on the fly.
Original idea/implementation - btc PR9298, backported and improved
* actually use bip39
* pbkdf2 test
* backport wallet-hd.py test
* Allow specifying hd seed, add dumphdseed rpc, fix bugs
- -hdseed cmd-line param to specify HD seed on wallet creation
- dumphdseed rpc to dump HD seed
- allow seed of any size
- fix dumpwallet rpc bug (wasn't decrypting HD seed)
- print HD seed and extended public masterkey on dumpwallet
* top up keypool on HD wallet encryption
* split HD chain: external/internal
* add missing cs_wallet lock in init.cpp
* fix `const char *` issues (use strings)
* default mnemonic passphrase is an empty string in all cases
* store mnemonic/mnemonicpassphrase
replace dumphdseed with dumphdinfo
* Add fCrypted flag to CHDChain
* prepare internal structures for multiple HD accounts
(plus some code cleanup)
* use secure allocator for storing sensitive HD data
* use secure strings for mnemonic(passphrase)
* small fix in GenerateNewHDChain
* use 24 words for mnemonic by default
* make sure mnemonic passphrase provided by user does not exceed 256 symbols
* more usage of secure allocators and memory_cleanse
* code cleanup
* rename: CSecureVector -> SecureVector
* add missing include
* fix warning in rpcdump.cpp
* refactor mnemonic_check (also fix a bug)
* move bip39 functions to CMnemonic
* Few fixes for CMnemonic:
- use `SecureVector` for data, bits, seed
- `Check` should return bool
* init vectors with desired size where possible
