Log wallet locks and unlocks.
Log wallet locks and unlocks.

Fixes #392.

jrick/btcwallet,Roasbeef/btcwallet,btcsuite/btcwallet,decred/dcrwallet,btcsuite/btcwallet,synrg-labs/btcwallet,Roasbeef/btcwallet,jrick/dcrwallet,Stash-Crypto/btcwallet,jrick/dcrwallet,synrg-labs/btcwallet,jrick/btcwallet,Stash-Crypto/btcwallet,decred/dcrwallet