Remove a bunch of explicit require_once

On a simple page (like forums home page) we goes from ~300 file loaded
to "only" 100 (still big but better than nothing).
From a perf point of view it goes from 0.15ms to 0.13ms
From a memory point of view it goes from 40MB to 16MB

Change-Id: Idc2eaa079b1a128f6fe6d49763118d22823a9392
Merge commit 'refs/changes/71/1371/5' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  Remove a bunch of explicit require_once

Conflicts:
	Makefile

Change-Id: I115010bb1f2c8fa96b60c510542099cbc9b3b7f4
This is Tuleap 6.6.99.18

Change-Id: I2ec74ff0da7e8a204ff5cfe73ce6ff8ebb8cc0f2