removed green border and fixed margin for windows

src/main/resources/css/light_theme.css

@@ -177,8 +177,8 @@
 
 /* windows needs an explicit border: */
 .main-window.os-windows {
-	-fx-border-color: TITLE_BG;
-	-fx-border-width: 1px;
+	-fx-border-color: CONTROL_BORDER_NORMAL;
+	-fx-border-width: 1px 0 0 0;
 }
 
 .main-window .button-bar {

src/main/resources/fxml/main_window.fxml

@@ -8,7 +8,7 @@
 		   fx:id="root"
 		   fx:controller="org.cryptomator.ui.mainwindow.MainWindowController"
 		   styleClass="main-window">
-	<VBox minWidth="650">
+	<VBox minWidth="600">
 		<SplitPane dividerPositions="0.33" orientation="HORIZONTAL" VBox.vgrow="ALWAYS">
 			<fx:include source="vault_list.fxml" SplitPane.resizableWithParent="false"/>
 			<fx:include source="vault_detail.fxml" SplitPane.resizableWithParent="true"/>

src/main/resources/fxml/vault_list.fxml

@@ -32,22 +32,18 @@
 			</VBox>
 		</StackPane>
 		<HBox styleClass="button-bar">
-			<HBox fx:id="addVaultButton" spacing="12" onMouseClicked="#toggleMenu" styleClass="button-left">
+			<HBox fx:id="addVaultButton" onMouseClicked="#toggleMenu" styleClass="button-left" alignment="CENTER" minWidth="20">
 				<padding>
 					<Insets topRightBottomLeft="12"/>
 				</padding>
-				<VBox alignment="CENTER" minWidth="20">
-					<FontAwesome5IconView glyph="PLUS" HBox.hgrow="NEVER" glyphSize="16"/>
-				</VBox>
+				<FontAwesome5IconView glyph="PLUS" HBox.hgrow="NEVER" glyphSize="16"/>
 			</HBox>
 			<Region HBox.hgrow="ALWAYS"/>
-			<HBox spacing="12" onMouseClicked="#showPreferences" styleClass="button-right">
+			<HBox onMouseClicked="#showPreferences" styleClass="button-right" alignment="CENTER" minWidth="20">
 				<padding>
 					<Insets topRightBottomLeft="12"/>
 				</padding>
-				<VBox alignment="CENTER" minWidth="20">
-					<FontAwesome5IconView glyph="COG" HBox.hgrow="NEVER" glyphSize="16"/>
-				</VBox>
+				<FontAwesome5IconView glyph="COG" HBox.hgrow="NEVER" glyphSize="16"/>
 			</HBox>
 		</HBox>
 	</VBox>