Logging improvements to Hyperopt

[vertti]

• Consider eval with zero trades made a failure. This way I was able to remove all the nan filtering etc.
• Log result string only when eval round is better than any before on this run, otherwise prints a dot.
• Make log results go to a new line so they align and are easy to read.
• Shorten and remove noise from logged lines from hyperopt.

After changes the logging normally looks like this:

.................
 5803/10000:    160 trades. Avg profit  0.45%. Total profit  0.00682250 BTC. Avg duration  43.6 mins.
.....................................................................................
 5889/10000:    178 trades. Avg profit  0.41%. Total profit  0.00682182 BTC. Avg duration  43.6 mins.
..................................

[gcarq]

I've left a minor comment, LGTM otherwise

[gcarq]

Comment is outdated

[vertti]

Thanks, fixed it.