Merge pull request #663 from Canaan-Creative/avalon4

Avalon4: Fix the default settings of new module, Fix MM4.1 voltage setting.
Add rudimentary avalon4 documentation
Update NEWS
Bump version to 4.9.0
Fix the matching_work count, display the small miner work count for debug
The temperature can be < 0C.
Update the default DH_DEC value from 0.1% to 0.2%