Experimental option to build blender as a python module, rather then blender embedding python.

CMake build option WITH_PYTHON_MODULE, will build ./bin/bpy.so

This allows 'bpy' to be imported from python or other applications/IDE's which embed python, eg:
   python -c "import bpy ; bpy.ops.render.render(write_still=True)"

This runs in background mode and has similar restrictions to running a script:
   blender --background --python test.py

TODO:
 - install to site-packages with blender scripts
 - add support for imp.reload()

source/creator/CMakeLists.txt

@@ -127,8 +127,21 @@ if(WITH_BUILDINFO)
 endif()
 
 # message(STATUS "Configuring blender")
+if(WITH_PYTHON_MODULE)
+	add_definitions(-DWITH_PYTHON_MODULE)
 
-add_executable(blender ${EXETYPE} ${SRC})
+	# creates ./bin/bpy.so which can be imported as a python module.
+	add_library(blender SHARED ${SRC})
+	set_target_properties(
+		blender
+		PROPERTIES
+			 PREFIX ""
+			 OUTPUT_NAME bpy
+			 LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin/
+	)
+else()
+	add_executable(blender ${EXETYPE} ${SRC})
+endif()
 
 # Post build steps for bundling/packaging.