Update quiver trace API for clarity and consistency

[emilykl]

Description

Following user feedback and internal testing of the quiver trace API, we plan to make some API updates for clarity and consistency with the rest of the plotly.js API:

• 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

Scope

• Update src/traces/quiver/attributes.js and src/traces/quiver/defaults.js
• Update other quiver trace logic which references the renamed attributes
• Update Jasmine tests and image mocks

[emilykl]

cc @degzhaus in case you have any thoughts on the above!