This change explains why Painless doesn't natively support datetime now, and
gives examples of how to create a version of now through user-defined
parameters.
This change abstracts the specific types away from the different
representations of datetime as a datetime representation in code can be all
kinds of different things. This defines the three most common types of
datetimes as numeric, string, and complex while outlining the type most
typically used for these as long, String, and ZonedDateTime, respectively.
Documentation uses the definitions while examples use the types. This makes
the documentation easier to consume especially for people from a non-Java
background.
James Rodewig
Nik Everett
Jack Conradson