[#9690] resource xdatetime fields: server-relative in db, offset-relative in view

* fields still initialized with server-relative times
* apply server_offset_time to view
* apply server_offset_time when setting hidden value - the value that goes back
  to the server, so that it is relative to server time
[#9690] make handling of server_offset_time consistent

* remove where not needed, now that times are stored without the offset
* use same logic to convert value to seconds when it's used
[#9690] fix date math to work with fractional hour offsets
fixes to users online grid

* add server_offset_time to displayed times
* fix query so that it actually displays the most recent activity of each user
add changelog entry for server_offset_time fixes
[#9690] Fix various issues with server_offset_time

Merge branch 'fixtimeoffset' into release-2.2

* fixtimeoffset:
  add changelog entry for server_offset_time fixes
  fixes to users online grid
  [#9690] fix date math to work with fractional hour offsets
  [#9690] make handling of server_offset_time consistent
  [#9690] resource xdatetime fields: server-relative in db, offset-relative in view