Capacity value in new AD tabs depends on the field capacity

Previously, this value was available only if a burndown field was created on the tracker.
Now, it directly uses the capacity field if exists.

Change-Id: I094bb12709b9b4a39fcd38c4f161c662c765f8f4
Merge commit 'refs/changes/66/666/4' of http://gerrit.tuleap.net/tuleap into tuleap-stable-master

* http://gerrit.tuleap.net/tuleap:
  Capacity value in new AD tabs depends on the field capacity

Change-Id: I264d34ca8952ab64e239430d16e118283a44f5ae
Tuleap 6.2.99.36

Change-Id: Ib0862a742a222e724b0ea57c137c11ff786b5e81