blender: add page (#1131)

Mostly based on https://www.blender.org/manual/advanced/command_line/arguments.html
with some additional help from http://blender.stackexchange.com/questions/3061/setting-render-options-from-the-command-line

pages/common/blender.md

@@ -0,0 +1,32 @@
+# blender
+
+> Command-line interface to the Blender 3D computer graphics application.
+> Arguments are executed in the order they are given.
+
+- Render all frames of an animation in the background, without loading the UI (output is saved to `/tmp`):
+
+`blender -b {{filename}}.blend -a`
+
+- Render an animation using a specific image naming pattern, in a path relative (`//`) to the .blend file:
+
+`blender -b {{filename}}.blend -o //{{render/frame_###.png}} -a`
+
+- Render the 10th frame of an animation as a single image, saved to an existing folder (absolute path):
+
+`blender -b {{filename}}.blend -o {{/path/to/output_folder}} -f {{10}}`
+
+- Render the second last frame in an animation as a JPEG image, saved to an existing folder (relative path):
+
+`blender -b {{filename}}.blend -o //{{output_folder}} -F {{JPEG}} -f {{-2}}`
+
+- Render the animation of a specific scene, starting at frame 10 and ending at frame 500:
+
+`blender -b {{filename}}.blend -S {{scene_name}} -s {{10}} -e {{500}} -a`
+
+- Render an animation at a specific resolution, by passing a Python expression:
+
+`blender -b {{filename}}.blend --python-expr '{{import bpy; bpy.data.scenes[0].render.resolution_percentage = 25}}' -a`
+
+- Start an interactive Blender session in the terminal with a python console (do `import bpy` after starting):
+
+`blender -b --python-console`