Write summary statistics to dbstats.json

[ArtPoon]

In dev branch these statistics are being calculated in make_beadplots but they are not being written to the JSON file:

covizu/batch.py

Lines 529 to 539 in 06848b3

	val['lineages'][lineage] = {
	'nsamples': len(samples),
	'lastcoldate': max(x['covv_collection_date'] for x in samples),
	'residual': residuals[lineage] if lineage in residuals else 0,
	'max_ndiffs': max(ndiffs),
	'mean_ndiffs': sum(ndiffs) / len(ndiffs),
	'mutations': mutations[lineage],
	'infections': infection_prediction[lineage]['infections'],
	'hunepi': infection_prediction[lineage]['hunepi'] if 'hunepi' in infection_prediction[lineage] else None,
	'raw_lineage': lname
	}