Relegate share notifications to -debug='stratum'

[maaku]

Right now any mining node's debug output is chock full of share notifications, if the miner requests a low difficulty. This ends up filling the log buffer and at some point the old history gets truncated. Share notifications are only really useful when debugging miner connections, so it should only be output when -debug='stratum is set.

[maaku]

As I think about this some more, share notifications might be useful to have in general, so long as they are limited in frequency. Maybe if a partial work gets above a critical threshold it is logged to the main log, instead of just the stratum log.