Fix request #7601 Security issue with legacy project creation page and IM plugin

- Remove the legacy project creation
- Slightly rewrite the "end of creation"

Change-Id: Ic26b345f26a02bc725fd577ba8290ae14ddbb5bf
Merge commit 'refs/changes/01/3201/3' of ssh://gerrit.tuleap.net:29418/tuleap into HEAD

* ssh://gerrit.tuleap.net:29418/tuleap:
  Fix request #7601 Security issue with legacy project creation page and IM plugin

Conflicts:
	src/common/autoload.php

Change-Id: I798cfc0689019935750a6b389e239d096c6d9270
This is Tuleap 7.6.99.52

Change-Id: I3729928939a2dc0b61bb452e9f5ba6f9aebfa742