time filter improvements (#3750)

* cleanup init

* add value support

* calendar time

* wip

* wip

* Refactor / cleanup date/time picker

* show hours and am/pm in description

* Pin filter popover to left side to prevent jumping

* misc styling tweaks

* unit picker should properly expand and collapse

* fix current unit toggle

* Let the DatePicker widget pick the default for date fields

* show calendar

* separate between

* fix styling on selection options

* fix pluralization

* fix operator selector

* Add dual calendar mode

* calendar behavior fixes

* calendar spacing

* tweak between view

* placeholder fix