css: update styles to new ui

Cleaned unused rules
Fixed rules to match GcalNewEventWidget

data/theme/gtk-styles.css

@@ -58,7 +58,7 @@
     border-radius: 0;
 }
 
-GtkOverlay > GtkButton {
+.new-event-widget > GtkButton {
     padding-top: 0px;
     padding-right: 0px;
     background-color: transparent;
@@ -66,23 +66,10 @@ GtkOverlay > GtkButton {
     border: 0;
 }
 
-.new-event-view {
-   padding: 18px;
+.arrow-bin {
     border: darker(@borders) 1px solid;
     color: @theme_fg_color;
     background-color: @theme_bg_color;
     -GcalArrowBin-arrow-size: 12px;
     -GcalArrowContainer-shadow-span: 3px;
 }
-
-.edit-dialog {
-  -GtkDialog-content-area-border: 0;
-  -GtkDialog-action-area-border: 18;
-}
-
-.readonly {
-  background-repeat: repeat;
-  background-image: linear-gradient(to bottom,
-                                    @borders,
-                                    shade(@theme_bg_color, 1.0));
-}