Reorganized the Freestyle Python API in a hierarchical package structure.

Both C- and Python-coded API components were rearranged into logical groups.
New Python modules are packaged as follows:

freestyle - Top-level package
freestyle.types - Classes for core data structues (e.g., view map)
freestyle.chainingiterators - Pre-defined chaining iterators
freestyle.functions - Pre-defined 0D and 1D functions
freestyle.predicates - Pre-defined 0D and 1D predicates
freestyle.shaders - Pre-defined stroke shaders
freestyle.utils - Utility functions

The Python modules are installed in scripts/freestyle/modules.  Pre-defined
styles are installed in scripts/freestyle/styles.

To-do: update styles according to the new Freestyle API package structure.

release/scripts/freestyle/styles/multiple_parameterization.py

@@ -0,0 +1,47 @@
+# ##### BEGIN GPL LICENSE BLOCK #####
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU General Public License
+#  as published by the Free Software Foundation; either version 2
+#  of the License, or (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software Foundation,
+#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+# ##### END GPL LICENSE BLOCK #####
+
+#  Filename : multiple_parameterization.py
+#  Author   : Stephane Grabli
+#  Date     : 04/08/2005
+#  Purpose  : The thickness and the color of the strokes vary continuously 
+#             independently from occlusions although only
+#             visible lines are actually drawn. This is equivalent
+#             to assigning the thickness using a parameterization covering
+#             the complete silhouette (visible+invisible) and drawing
+#             the strokes using a second parameterization that only
+#             covers the visible portions.
+
+from freestyle import ChainSilhouetteIterator, ConstantColorShader, IncreasingColorShader, \
+    IncreasingThicknessShader, Operators, QuantitativeInvisibilityUP1D, SamplingShader, \
+    TextureAssignerShader, TrueUP1D
+from shaders import pyHLRShader
+
+Operators.select(QuantitativeInvisibilityUP1D(0))
+## Chain following the same nature, but without the restriction
+## of staying inside the selection (0).
+Operators.bidirectional_chain(ChainSilhouetteIterator(0))
+shaders_list = [
+    SamplingShader(20),
+    IncreasingThicknessShader(1.5, 30),
+    ConstantColorShader(0.0, 0.0, 0.0),
+    IncreasingColorShader(1, 0, 0, 1, 0, 1, 0, 1),
+    TextureAssignerShader(-1),
+    pyHLRShader(), ## this shader draws only visible portions
+    ]
+Operators.create(TrueUP1D(), shaders_list)