update main.h

Added CUTOFF_POW_BLOCK = 30000 - this had been removed from the master for some reason.
Check PoW has reached block 30,000 fix PoS
Updated Version numbers
MinAge for PoS 12hrs MaxAge 56d
Cutoff_pow_block=13900
Update main.cpp
updated POW - 13900
Merge pull request #2 from alcamie101/readd-PoW-check

Readd po w check