Manipulator: Python API

Initial support for Python/Manipulator integration
from 'custom-manipulators' branch.

Supports:

- Registering custom manipulators & manipulator-groups.
- Modifying RNA properties, custom values via get/set callbacks,
  or invoking an operator.
- Drawing shape presets for Python defined manipulators (arrow, circle, face-maps)

Limitations:

- Only float properties supported.
- Drawing only supported via shape presets.
  (we'll likely want a way to define custom geometry or draw directly).
- When to refresh, recalculate manipulators will likely need
  integration with notifier system.

Development will be continued in the 2.8 branch

doc/python_api/examples/bpy.types.ManipulatorGroup.py

@@ -0,0 +1,29 @@
+"""
+Manipulator Overview
+--------------------
+
+Manipulators are created using two classes.
+
+- :class:`bpy.types.ManipulatorGroup` - stores a list of manipulators.
+
+  The manipulator group is associated with a space and region type.
+- :class:`bpy.types.Manipulator` - a single item which can be used.
+
+  Each manipulator group has a collection of manipulators which it manages.
+
+The following example shows a manipulator group with a single,
+manipulator used to control a lamp objects energy.
+
+.. literalinclude:: __/__/__/release/scripts/templates_py/manipulator_simple.py
+
+
+It's also possible to use a manipulator to run an operator.
+
+.. literalinclude:: __/__/__/release/scripts/templates_py/manipulator_operator_target.py
+
+This more comprehensive example shows how an operator can create a temporary manipulator group to adjust its settings.
+
+.. literalinclude:: __/__/__/release/scripts/templates_py/manipulator_operator.py
+
+"""
+