Support method to get views/downloads for a record

[eblondel]

The record stats will be added as record field, together with a method getStats(). The stats will also appear when printing the record object as following:

....|-- stats:
    ↓ downloads = 10
    ↓ unique_downloads = 6
    ↓ version_downloads = 1032
    ↓ version_unique_downloads = 356
    👁 unique_views = 15
    👁 version_unique_views = 820
    👁 version_views = 1028
    👁 views = 16
    ■ version_volume = 36076341
    ■ volume = 223780