Flatten button styles in flat.css theme

Author: Kristan Kenney

install/deb/themes/flat.css

@@ -73,4 +73,13 @@ b, strong {
 
 .vst-textinput {
     box-shadow: none;
+}
+
+.ui-button, .button {
+    box-shadow: none !important;
+    background: linear-gradient(to bottom, rgba(235,243,249,1) 0%,rgba(223,235,245,1) 100%) !important;
+}
+
+.ui-button.cancel, .button.cancel {
+    background: linear-gradient(to bottom, rgba(250,250,250,1) 0%,rgba(241,241,241,1) 100%) !important;
 }