Remove default cross tracker search

Default cross tracker search (without any criterion) is highly inefficient
due to the monstro-query AND display of a lot of artifacts in hierarchy
(no pagination + js rendering of tree).

We remove this feature to avoid bad user experience to users:
- very long page load
- impact on other users (mysql loaded by monstro query)

Change-Id: I1ad0094c150e235a20a4ef50eb5a736516c18795
Merge commit 'refs/changes/68/668/1' of http://gerrit.tuleap.net/tuleap into HEAD

* http://gerrit.tuleap.net/tuleap:
  Remove default cross tracker search

Change-Id: I3307343421eb44b8f8215db664874c5019bf69a2
This is Tuleap 6.2.99.41

Change-Id: I3cd29526262ee69115485256f878232969e403f0