ui: fixed ui issues

* fixed dock title buttons on bottom on Windows
* fixed no gap between buttons on Linux
* fixed dark scheme title bar contrast
* fixed filter checkbox colors for dark schemes

bin/app/data/gui/main/main.css

@@ -25,7 +25,15 @@ QDockWidget::title {
 
 QDockWidget::close-button, QDockWidget::float-button {
 	background: transparent;
-	border: none;
+	border: <platform_wml:0|0|1>px solid transparent;
 	icon-size: 12px;
-	margin-top: 2px;
+	margin-top: <platform_wml:0|2|2>px;
+}
+
+QDockWidget::close-button {
+	margin-left: <platform_wml:0|2|0>px;
+}
+
+QDockWidget::float-button {
+	margin-right: <platform_wml:0|2|0>px;
 }

bin/app/data/gui/tabbed_view/tabbed_view.css

@@ -86,6 +86,10 @@ QTableView QTableCornerButton::section {
 	border-top-left-radius: 10px;
 }
 
+QCheckBox {
+	color: <color:table/text/normal>;
+}
+
 #help_button {
 	background: transparent;
 	border: none;