1.3.0: GTK+3 theme improvements

* 3108c48 fix(change_color): remove Makefile and scss sources from the generated theme
* a2ccf03 fix(gtk3.20: choosers): fix colorswatch button
* ce491ce fix(gtk3.20: view): fix inset/outset/groove/ridge frames
* 5f577dd fix(gtk3*: assets): almost missing borders for checkboxes and radios (especially in dark colorschemes)
* 196acd6 fix(gtk3.20: entry): not-focused entry border color