This also brings in various associated changes to the FFI methods in
zcash-light-client-kit as a result of moving to the main branch of
zcash/librustzcash.
Closes#381
This commit brings a Zatoshi type developed on the Secant project,
helper classes like Clamped and tests.
Zatoshi has been incorporated as a Codable type for SQLite Swift
to allow serialization into the pending database.
FIXES on Demo App
fix comments