Create a command for GOP calculation

[rguliev]

INPUT

1. I asked Povey about our GOP calculation at google groups. Seems like it is ok.
2. We have a function compute_gmm_probs which calculates probs for a GMM model.
3. An article about GOP calculation: here

OUTPUT
A cli command calculate_gop with
arguments:

• a folder of a gmm model

options:

• --per-phone - will calculate GOP for each phoneme, and otherwise it calculates overall GOP

output

• without --per-phone (by default): one number — overall GOP
• with --per-phone: one row for each phone GOP in format <phone symb><whitespace><GOP value>

TODO

• Add a calculate_gop helper function
• Write a cli working script

[rguliev]

I was not able to implement the metric directly from the article. Instead, I used:
PER (Phoneme Error Rate) = number of frames with correct prediction / total number of frames
I added analize_phone_errors cli command, which calculates PER along with other metrics in three versions: overall, per phoneme (i.e. grouped by phoneme), per utterance and outputs them in csv format.