add RPY parameter handling

[dvanthienen]

This PR allows a tf frame to be published to be defined in a yaml file using the RPY syntax:

tf_frame_to_be_published_parameter_name/header/frame_id: "parent_frame_id"
tf_frame_to_be_published_parameter_name/child_frame_id: "child_frame_id"
tf_frame_to_be_published_parameter_name/transform/translation/x: 0.0
tf_frame_to_be_published_parameter_name/transform/translation/y: 0.0
tf_frame_to_be_published_parameter_name/transform/translation/z: 0.0
tf_frame_to_be_published_parameter_name/transform/rotation/R: deg(0.0)
tf_frame_to_be_published_parameter_name/transform/rotation/P: deg(0.0)
tf_frame_to_be_published_parameter_name/transform/rotation/Y: deg(0.0)

Next to the existing syntax with quaternions:

tf_frame_to_be_published_parameter_name/header/frame_id: "parent_frame_id"
tf_frame_to_be_published_parameter_name/child_frame_id: "child_frame_id"
tf_frame_to_be_published_parameter_name/transform/translation/x: 0.0
tf_frame_to_be_published_parameter_name/transform/translation/y: 0.0
tf_frame_to_be_published_parameter_name/transform/translation/z: 0.0
tf_frame_to_be_published_parameter_name/transform/rotation/x: 0.0
tf_frame_to_be_published_parameter_name/transform/rotation/y: 0.0
tf_frame_to_be_published_parameter_name/transform/rotation/z: 0.0
tf_frame_to_be_published_parameter_name/transform/rotation/w: 1.0

[tfoote]

This looks good now. It just needs at least a basic test.

[ahcorde]

This PR is targeting a EOL distribution melodic, closing this PR, feel free to reopen this against a maintained branch