[Core][Tests][Build] Add BIP39,BIP44 Support and CMake Build support

[akshaynexus]

Notable Changes / Release Notes:

[Core]

• Definition of new int var nExtCoinType (for BIP44).
• minimal BIP32 changes backported from Bitcoin upstream;
• BIP44 derivation scheme;
• BIP39 mnemonic and mnemonic passphrase can be used to create HD wallet (optional, using random mnemonic and mnemonic passphrase if mnemonic was not specified by the user explicitly);
• Only seed is stored, all keys are derived on the fly (seed is stored encrypted if wallet is locked).
• Definition of new dumpwallethd command to dump walllet info with hdchain info.
• Refactor of ui_interface.h to guiinterface.h.
• Update db.h and db.c to PIVX Upstream.
• Definition of new startup args for dogecashd :usehd,hdseed.mnemonicpassphrase.
• [Staking] Prevent potential negative out values during stake splitting.
• Remove unused EXT_COIN_TYPE from chainparams.
• Definition of GetScriptForRawPubKey, used for HDChain code.

[Tests]

• Add updates to test_runner.py from PIVX.
• Add wallet_hd.py test.
• Fix keypool size asserts in tests.

[Build]

• Add CMake Support,cherrypicked from PIVX.