Add waveqlab3d reader for surface waveforms

[baagaard-usgs]

Add reader for surface waveform output from waveqlab3d ground-motion simulation software.

Metadata

Use YAML file for metadata. The raw waveqlab3d data files do not contain any metadata.

• crs Coordinate system as Proj parameters, WTK, or EPSG code
• origin_x X coordinate of grid origin in CRS coordinate system
• origin_y Y coordinate of grid origin in CRS coordinate system
• endian_type Endian type of floating point values in raw data files
• filenames Template for forming filenames of raw data files {component}=x,y
• num_x Number of grid points in the x coordinate direction
• num_y Number of grid points in the y coordinate direction
• horizontal_resolution Horizontal grid spacing in meters.
• num_timesteps Number of time steps in raw data files.
• time_step Time step in raw data files.
• start_time UTC data time of first time step.

Raw data

• Velocity in m/s.
• 64-bit floating point values.
• Each component in a different file.