xml/schema/Timetrack/Task.xml: task lead is not a mandatory field.
templates/CRM/Timetrack/Form/Task.tpl: added autocomplete on the Task lead field.
CRM/Timetrack/Form/Task.php: after postProcess, redirect back to the case, instead of semi-randomly redirecting using popUserContext.
CRM/Timetrack/PseudoConstant.php: added getTaskStatuses().
CRM/Timetrack/Case/Page/CaseView.php: show textual task statuses.
CRM/Timetrack/Case/Page/CaseView.php: mini cleanup.