Add MultiPV support to uci.SearchResults

[cmitsakis]

I added some more commits to PR #100
closes #99

In kmorrison's PR, I noticed is that if you do a MultiPV search, eng.SearchResults().Info shows the score of the last MultiPV result which is the worst move, so the score is wrong. I fixed this issue.

I also changed the type of MultiPV from []*Info to []Info.

[cmitsakis]

kmorrison's implementation assumes the info line with multipv 1 is printed before the others. This is probably always true in practice, but the UCI protocol does not require it's printed first. It doesn't specify any order. It only requires they are in consecutive lines. I can fix this if you think it's an issue worth fixing.

[valentinEmpy]

Any progress on merging this?
It'd be extremely useful.

[kogan69]

Hi, everyone!
Any idea when it will be merged into master?
I wait for it impatiently :)
Thanks a lot!