Renaming yaml fields and supporting multiple topics

[RValner]

Just as a reference, here's an example of how the yaml file currently is structured:

Plugins:
- type: "image"
  class_name: "rviz/Image"
  rviz_name: "Temoto Image"
  data_type: "sensor_msgs/Image"

- type: "laser_scan"
  class_name: "rviz/LaserScan"
  rviz_name: "Temoto Laser Scan"
  data_type: "sensor_msgs/LaserScan" 

So the first problem is that the field names in the yaml description are quite confusing, so i propose:

• we should get rid of the type
• class_name -> plugin_name
• rviz_name -> name_seen_by_user
• data_type -> visualized_data

Which brings us to the second issue, lack of support for multiple topics, thus I think the visualized_data should be a vector of key value pairs (example):

visualized_data:
  - laserscan: "sensor_msgs/LaserScan"

or

visualized_data:
  - panospheric_image_front: "sensor_msgs/Image"
  - panospheric_image_back: "sensor_msgs/Image"

This would require some changes both in the visualization_manager.cpp and visualization_manager_interface.h so that user can specify the topics.