support reindex release

fixes error reporting when launching full nodes with config reindex=1, which supports uplevel apps like wallet , blockchain explorers, etc.

v0.12.1-btcnano

The btcnano blocks the browser's underlying execution script.

First release

After testing, this release fixed bugs(maybe temporarily) below:
1.headers not continuous error, in net_process.cpp
2.add hashReserved part in getblock rpc call
3.deleted debug outputs from hash.h and net_process.cpp
4.replaced names to, like 'Nano'