Log Message:
gallery-dl: Update to 1.16.0

Changes:
1.16.0
------
### Additions
 - [booru] implement generalized extractors for `*booru` and `moebooru` sites
   - add support for sakugabooru.com (#1136)
   - add support for lolibooru.moe (#1050)
   - provide formattable `date` metadata fields (#1138)
 - [postprocessor:metadata] add `event` and `filename` options (#315, #866, #984)
 - [postprocessor:exec] add `event` option (#992)

### Changes
 - [flickr] update default directories and improve metadata consistency (#828)
 - [sankaku] use API endpoints from `beta.sankakucomplex.com`
 - [downloader:http] improve filename extension handling (#776)
 - replace all JPEG filename extensions with `jpg` by default

### Fixes
 - [hentainexus] fix extraction (#1166)
 - [instagram] rewrite (#1113, #1122, #1128, #1130, #1149)
 - [mangadex] handle external chapters (#1154)
 - [nozomi] handle empty `date` fields  (#1163)
 - [paheal] create directory for each post (#1147)
 - [piczel] update API URLs
 - [twitter] update image URL format (#1145)
 - [twitter] improve `x-csrf-token` header handling (#1170)
 - [webtoons] update `ageGate` cookies

### Removals
 - [sankaku] remove login support