Enrichment documentation

[mmcauliffe]

Finish comprehensive pass over enrichment functionality in PolyglotDB.

[msonderegger]

Details from the to-do google doc:

• Enrichment section probably could use some better explanation of algorithms includes:
• max onset for syllables, what the custom formant algorithm is doing, what utterance deteremination is doing (some of this is in tutorials, could be moved)
• “also the full detail of utterances with min pause length and min utterance length and their interactions”
• “also algorithms for pitch, with the speaker adjusted option”
• minimum here: fill out things to be filled in (in documentation).. others can fill in but MM knows full list.