[Explore View] Make Time selections more usable

[vylc]

Updates to make filtering on time more efficient:
(1) Default to 'Relative' tab. Allow the user choose commonly used time frames (ie. last week, last month, etc.)
(2) After clicking on either Since or Until, there should be affordances to modify both Since and Until values at the same time
(3) Freeform and Fixed can be combined. Get to these options by clicking on the tab.
(4) Once the date/time has been selected on the calendar popup, it should close to avoid multiple windows showing up
(5) OK button to be moved to lower right corner as standard UI design pattern (not shown, but 'Cancel' should be to the left of OK and should be a white button, black/grey text.
(6) Allow type in for fixed dates - currently limited to just being able to select from calendar popup

Make sure these boxes are checked before submitting your issue - thank you!

• I have checked the superset logs for python stacktraces and included it here as text if any
• I have reproduced the issue with at least the latest released version of superset
• I have checked the issue tracker for the same issue and I haven't found one similar

Superset version

0.23.0rc1

Expected results

Actual results

Steps to reproduce

[betodealmeida]

@vylc, a few questions about this:

I understand that in this new design the relative tab sets both the since and until fields. How does this work? If I select "last week" will this set since to -7 days and until to now?

What happens if I then click until and make a new selection, say, "last day"? Will this set since to -1 day and until to now? Or is the time range now from -7 days to -1 day?

[vylc]

Good question. Since we are overhauling, maybe we just get rid of the Until selection altogether and do something like this

So the user can override the Until through that input box below. By default, we set it to now, but they can do some sort of free form text to specify. Thoughts?

[vylc]

Done