Add TaskService

This adds tasks service to Redfish and creates an
example for crashdump. The TaskData object creates
tasks that can be updated based on d-bus matches. It
also has a configurable timeout using timers. Task
Monitor uses these task objects to reply with a 202
until the async task is done, then a 204 when it is
either failed or completed.

Messages support will come in future commit.

Tested: Validator passed, wrote script to poll monitor,
verified that got 202 with location header and retry-after
set correctly, then 204, then 404.

Change-Id: I109e671baa1c1eeff1a11ae578e7361bf6ef9f14
Signed-off-by: James Feist <james.feist@linux.intel.com>