This doesn't affect Sapling note detection (which uses Compact Blocks),
but enables the enhancement logic to decrypt and store the corresponding
transactions for displaying memo fields.
The binary itself was removed in zcash/zcash-android-wallet-sdk#263 but
the `Cargo.toml` was not updated. This didn't affect the SDK itself
because by default it didn't build with the `updater` feature flag.
Move SDK from the root gradle project to its own Gradle module
Move the demo app to be a peer of the SDK
This will simplify integration with CI on Bitrise.
Jack Grigg
Carter Jernigan