Improve lattice view styles

[gwwatkin]

Issue Description

The lattice looks very boxy and clunky, we want it to look more professional.

Proposed Solution

Examples of things to do:

• Legend/Explanation:
  • what is a cell? (show a surface code patch)
  • what are boundaries?
  • what are the numbers that show up in the cells?
  • explain colors
  • an interactive description of the lattice view
• Fix corners of cells
  
• Implement navigation of large lattices #18

Please add more ideas @Keelando and @alexnguyenn