Expose logging macros in rclpy

[dhood]

meta-ticket.

First question: which usage do we want with respect to the severity:

1. loginfo(...) (like in ROS 1)
2. log(..., severity=INFO)

Second question: when considering the other logging variations, which do we want?

1. log_info_throttle_named(...) (like the C usage)
2. log_info(..., throttle_duration=1.0, name='my_name') (more pythonic IMO)

[dirk-thomas]

We talked about this in the meeting:

Regarding the first question: use 2. log(..., severity=INFO) but offer 1. loginfo(...) for convenience.

Regarding the second question: the keyword argument (2.) is preferred.

Additionally it would be nice to have a get_named_logger(name='xxx') which can be called once and then be passed around. That logger could have log(..., severity=INFO) as well as info(...) for convenience.

[mikaelarguedas]

closing this now that #102 has been merged