Add BASE and WAIST to humanoids visualization

[ekaszubski]

Need to determine how/where to specify ground plane. Ground plane transform sensor -> ground plane must be provided to Humanoid::getJoint( BASE, transform ) <- VisualizationAdapter<Humanoid> [ <- VisualizationAdapter<Humanoids>, ... ] <- SemioVisualizationServerNode.

Also need to explicitly request BASE and WAIST in VisualizationAdapter<Humanoid>; need to determine when/how to specify that this should happen.

[ekaszubski]

Proposal:

• Always try to draw WAIST frame
• Look up a /sensor -> /world transform; if it exists, try to draw BASE, using the transform data as the ground plane; otherwise do not draw BASE

[ekaszubski]

Implementing in #18

[rossmead]

Let's commit to there always being a world frame -- by default, the sensor is at the same pose as

The base pose then always has z=0 w.r.t. the world frame.

Alternatively (but least desirable in my opinion) is to simply set the base pose to being the same as either the waist or the torso (in order of preference).

In short, I'd like to treat base pose as being fundamental to the person so we can be assume that it's always there.

[ekaszubski]

Updated proposal:

• Always try to draw WAIST frame
• Look up a /sensor -> /world transform; if it exists, try to draw BASE using the transform data as the ground plane; otherwise try to draw BASE using the default zero transform

[rossmead]

^ Looks good. :-)

[ekaszubski]

Implemented in #18