Some UI Quibbles

[snwh]

• the Save as button could be moved to the headerbar as a primary action and use text instead of an icon so it is more clear

• the precision and features headings should use the heading class instead of title-2
  

• it is unclear what "Precision" means (is this the most accurate term for what this slider affects?) and the numbers do not convey meaning--what does "precision = 0" mean? This might be solved by defining the two extremes with a string label.

• the big list of switches under Features is pretty cumbersome, it might be nice to break them into groups of related options to make it a bit more understandable