Discover time segements

[#1]

In Discover it would be really useful to be able to create segments based on time, independent of date, eg. lunchtime each day. If you could also create them so that they applied to days of the week that would be even better. It means we could see how people behaved durring office hours that may be different from evening or weekend behaviour.

[#2]

It would be nice as a default, as opposed to having to use the Time Part plugin or having to set your own eVars and props.

[#3]

We used a slightly different approach for this:

- A VISTA rule populates a single prop with a timestamp of the most recent 15 minute time period (e.g. June 1 11:00 PM -- but as GMT timestamp)

- SAINT classification categorizes the timestamp by day, hour, weekday/weekend, section of day (e.g. early morning, business hours, etc). We also used this to "time shift" to different time zones.