Add a find-blunders method

[artasparks]

This PR fleshes out the FindBlunders method. It's not very configurable, but it does work end-to-end

Example test-run:

kashomon@Joshs-Air:~/inprogress/clamshell (blunders)$ go run katalyze/main.go --config=katalyze/testdata/analysis_example.cfg --model=katalyze/testdata/g170e-b10c128-s1141046784-d204142634.bin.gz katalyze/testdata/example-game.sgf
I1125 21:36:17.982544   83641 katago.go:68] Starting Katago analyzer
I1125 21:36:17.982660   83641 katago.go:69] Using model "katalyze/testdata/g170e-b10c128-s1141046784-d204142634.bin.gz"
I1125 21:36:17.982685   83641 katago.go:70] Using gtp config "katalyze/testdata/analysis_example.cfg"
I1125 21:36:25.707929   83641 katago.go:87] Katago Startup Complete
I1125 21:36:25.707978   83641 main.go:103] using files [katalyze/testdata/example-game.sgf]
I1125 21:36:25.708011   83641 main.go:105] Processing file "katalyze/testdata/example-game.sgf"
I1125 21:36:39.888000   83641 main.go:126] Finished processing file "katalyze/testdata/example-game.sgf"
I1125 21:36:39.888056   83641 main.go:133] Finished adding to game for file "katalyze/testdata/example-game.sgf"
I1125 21:36:39.888253   83641 main.go:146] Found Positions: [.0:64 .0:72 .0:80 .0:86 .0:92 .0:96 .0:100 .0:108 .0:122 .0:124 .0:134 .0:138]
I1125 21:36:39.888303   83641 katago.go:196] Shutting down Katago analyzer

Some miscellaneous changes:

• Make a treepath-clone helper
• Add better input-validation for katalyze main.go
• Fix flag: analysisThreads => analysis_threads

[mhoak]

LGTM.

It might be nice for FindBlunders to return something that has treepath and point-value of blunders. That way we can start to understand if there is any correlation between point-value and usefulness of problems.

[artasparks]

It might be nice for FindBlunders to return something that has treepath and point-value of blunders.

That's a good idea. Filed #155