Subaddresses (Part 1) merged

FYI, the first stable part of "subaddresses" code has been merged to master branch at Github. This is mainly for early user experiments and GUI wallet design.

Please refer to PR #28 for usage: https://github.com/sumoprojects/sumokoin/pull/28

As current wallet version doesn't recognize subaddresses as valid ones, please DO NOT use subaddresses for:

• Withdrawal from exchanges
• Mining receipt addresses
• Sending funds to them from old (cli/GUI) wallets

Subaddresses (Part 2):

- Support sending to multiple subaddresses or mix of sub/primary addresses
- Improve scanning speed and stability

Expected release date: By Nov 30, 2017

After full-featured subaddresses code is completely merged, binaries will be officially bumped to version v.0.2 (code name: Sapporo)

GUI wallet with subaddresses:

Design target: Simplifying user experience with pre/auto subaddresses generation. User can freely pick any unused subaddress for receiving fund without revealing true main address.

Expected release date: In December 2017