Calculate time-difference when new entries are being added

[enriquezrene]

As a user I want to see the time difference (hh:mm) of the time-entry I am creating so I can know how much time I spent in a task.

Acceptance Criteria

• time-entries page display the time difference (time out - time in) when a new time entry is being created/updated
• Refer to the attached image for a reference (Total Hours section)