[services] Expose services exposed by robots in details request

Part of #299
[pymorse] Export robot services as method

Fix #299
Try to use default interface whenever possible

When setting a default interface to a robot, and adding a component
that is not declared in builder/data.py, it fails.

This commit tries to use, if it exists, the default method of the datastream mw.

Typical scenario: you develop a new component out-of-tree. You want to
test it/debug it with the socket interface. It may work out-of-the-box
(we still display a warning, though).
[builder] Allow to call SensorCreator/ActuatorCreator with a class

...instead of a classpath

This allows to easily use custom components:
- you write them by inheriting morse.core.{actuator|sensor}
- in your Builder script, you import the component (-> do not import bge
  at module level!)
- you wrap it with {Actuator|Sensor}Creator

Example:

from morse.builder import *
from actuator.my_actuator import MyActuator

robot = ATRV()
toto = ActuatorCreator(MyActuator) # the class, not an instance!
robot.append(toto)

This only works for 'mesh-less' (ie, pure python) component.