Added

Support for working with IListItem attachments [jansenbe - Bert Jansen]
Page scheduling support: enable a pages library for page publish scheduling and schedule the publishing of a page [jansenbe - Bert Jansen]
IsSubSite methods on IWeb [jansenbe - Bert Jansen]
Support for converting the site's datetime to UTC and vice versa [jansenbe - Bert Jansen]
Using @mentioning in page/listitem comments and replies [jansenbe - Bert Jansen]
Support for downloading versions of a file #483 [DaleyKD - Kyle Daley]
Support for ListItem versions #481 [DaleyKD - Kyle Daley]
Support for liking/unliking pages + adding/deleting comments and comment replies + like/unlike these comments on pages [jansenbe - Bert Jansen]
Support for adding/deleting comments and comment replies + like/unlike these comments on list items [jansenbe - Bert Jansen]

Changed

Reliabilty update when parsing taxonomy field json [jansenbe - Bert Jansen]
Throw exception when using a REST based list item add/update while only the user id is specified [jansenbe - Bert Jansen]
"Special" field value types (User, Lookup, Url, Taxonomy) were wrongly marked as changed on data load causing blanking out data with item updates [jansenbe - Bert Jansen]
Fixed the SharePoint Syntex ClassifyAndExtract functionality to skip folders and work well with large lists [jansenbe - Bert Jansen]
Fixed issue when using AddValidateUpdateItemUsingPath (used for IlistItem adds) is returning a field level add error - now an exception is thrown [jansenbe - Bert Jansen]
Fixed memory leaks for use cases that resulted in repeated creation of the Azure AppInsights TelemetryClient [jansenbe - Bert Jansen]
Fixed bug that resulted in an unneeded query due to paging #486 [PaoloPia - Paolo Pialorsi]