Quark v0.10.6.1 - POS/POW hybrid for Quark

https://github.com/quark-project/quark/releases/tag/v0.10.6.1

POS parameters:
- 3.5% pa POS interest
- 30 days minimum stake age
- Activates block 4937000 (est 25 Nov 2017)

POS staking is enbled by default. To prevent staking use -reservebalance=x (where x is amount to reserve for non-staking) or -staking=0 parameter.

Upgrade notes:
- Backup your Quark data directory before upgrading (in particular your wallet.dat)
- A database reindex is required the first time Quark 0.10.6 is run on an old installation, e.g.
   run qt with:  quark-qt -reindex
   run daemon with: quarkd -reindex --daemon
   or click OK on the prompt to rebuild database.
   Note: This can take a few hours.