Improve support non-base types

[hadley]

This is a meta issue related for all bind/grouped-mutate/join/filter issues related to custom S3 + S4 classes

• chron (dplyr bind_rows coerces inputs where data.table rbindlist does not #1829)
• lubridate (filter on lubridate interval does not filter start slot #1581, bind_rows does not preserve lubridate interval class #1708, Add warning when two different timezones are joined #3059)
• difftime (Operations involving group_by() can corrupt difftime values due to mixing up units. #2059)
• table (bind_rows() with columns of class "table" #2406)
• POSIXct (timezones are lost sometimes, when using bind_rows #2322)
• bit64 (left_join() with bit64 columns translates NA incorrectly #3210)

See also r-lib/vctrs#27

[krlmlr]

Should be implemented in vctrs.