restructure the theme to use a SASS workflow
provide custom sass functions for gtk equivalents

- generally sass has equivalents of gtk functions for mixing color
  in the case of the spinner though, the currentColor only lives
  in the context of gtk runtime. gtkalpha() is a way to provide
  alpha() in gtk context rather than SASS alpha()
fist test of mixins
buttons mixin testbed
use extends for linked buttons/entries
focus for entries using box-shadow (extended)
subtle gradients for entries. tango selection color
comboboxes. slightly less obnoxious pushed state for buttons
base headerbar style
not sure if we need mixins for the linear gradients

- lapo suggests being more fine grained with the generic
  drawing routines/mixins, but in the end you're not saving
  on repetition much. We'll see
use mixins to get generic button drawing
button sizing
contain stylesheets in the gresource

- it's all or nothing, everything needs to live in a gresource
add destructive action.

- done legibly using @each with multi-lists (needs SASS 3.3)
duh, forgot to add the contained SCSS files
buttons: backdrop:active state colors
headerbar backdrop is flat
proper window frames using box shadows
selection mode headerbar

- very preliminary
make mult-linked buttons work