Added exception to the LICENSE file which applies to test models.

git-svn-id: https://assimp.svn.sourceforge.net/svnroot/assimp/trunk@270 67173fc5-114c-0410-ac8e-9d2fd5bffc1f

LICENSE

@@ -1,5 +1,3 @@
-Open Asset Import Library (ASSIMP)
-----------------------------------------------------------------------
 
 Copyright (c) 2006-2008, ASSIMP Development Team
 All rights reserved.
@@ -33,3 +31,13 @@ DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+
+----------------------------------------------------------------------
+AN EXCEPTION applies to all files in the ./test/models subfolder.
+These are 3d models for testing purposes, from various free sources
+on the internet. They are - unless otherwise stated - copyright of
+their respective creators. For a specific 3d model, see 
+<model>.source.txt for more legal information.
+----------------------------------------------------------------------