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/haloing.py

@@ -0,0 +1,46 @@
+# ##### 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 : haloing.py
+#  Author   : Stephane Grabli
+#  Date     : 04/08/2005
+#  Purpose  : This style module selects the lines that 
+#             are connected (in the image) to a specific 
+#             object and trims them in order to produce
+#             a haloing effect around the target shape
+
+from freestyle import ChainSilhouetteIterator, Id, IncreasingColorShader, IncreasingThicknessShader, \
+    Operators, QuantitativeInvisibilityUP1D, SamplingShader, TipRemoverShader, TrueUP1D
+from PredicatesU1D import pyIsOccludedByUP1D
+from logical_operators import AndUP1D, NotUP1D
+from shaders import pyTVertexRemoverShader
+
+# id corresponds to the id of the target object 
+# (accessed by SHIFT+click)
+id = Id(3,0)
+upred = AndUP1D(QuantitativeInvisibilityUP1D(0), pyIsOccludedByUP1D(id))
+Operators.select(upred)
+Operators.bidirectional_chain(ChainSilhouetteIterator(), NotUP1D(upred))
+shaders_list = [
+    IncreasingThicknessShader(3, 5), 
+    IncreasingColorShader(1,0,0, 1,0,1,0,1),
+    SamplingShader(1.0),
+    pyTVertexRemoverShader(),
+    TipRemoverShader(3.0),
+    ]
+Operators.create(TrueUP1D(), shaders_list)