Update documentation that work log entries are stored in UTC Server System Time.

Summary: Our documentation does not clear state in either the [User Profile| or Logging work or User Profile Timezone that the worklog data is not stored according to the user profile time zone but specific to the server timezone (UTC).

Problem Definition:
This can create confusing results when users from different time zones are entering time. It is hard to gauge without some manual conversion what time they actually. In some cases it can throw the figure off by day i.e. 10/31/2017 5 PM PST Converts to 11/01/2017 2:00 AM CET.

Suggested Solution:
Update documentation to reflect how work log data is actually stored.

Why this is important:
This creates a lot of confusion when tracking time within JIRA. JIRA treats it as the long entry as an absolute point that is stored in UTC as reflected by the developers comment on JRA-35503