[tools] Add wallet inspection and modification tool

This commit adds wallet-tool, a tool for creating and interacting with
wallet files. Original implementation was by Jonas Schnelli
<dev@jonasschnelli.ch> with modifications by John Newbery
<john@johnnewbery.com>

MSVC files were provided by Chun Kuan Lee <ken2812221@gmail.com>:

build: Add MSVC project files for bitcoin-wallet-tool

.gitignore

@@ -5,6 +5,7 @@ src/bitcoin
 src/bitcoind
 src/bitcoin-cli
 src/bitcoin-tx
+src/bitcoin-wallet
 src/test/test_bitcoin
 src/test/test_bitcoin_fuzzy
 src/qt/test/test_bitcoin-qt