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