Update quiver trace API

[emilykl]

Closes #7944

• rename sizeref attribute to lengthfactor (since sizeref for other traces works differently, as a divisor rather than a multiplier, we shouldn't use the same name here)
• rename sizemode to lengthmode (to parallel lengthfactor and because it's really about vector length rather than size)
  • accepted values 'scaled' and 'raw' remain the same
• rename anglemode to uvref
  • accepted values 'data' and 'paper' remain the same

Also:

• Fix incorrect default for uvref (was 'axis' which is not an accepted value; changed to 'data')
• Update Jasmine tests and image tests accordingly
• Update some other attribute descriptions