QML-UI: add more properties to Units and Theme

- colors for accentuation (background and text)
- text color to paint on highlights
- units.spacing (derived from gridUnit, so it's dpi-corrected)
- port main.qml, especially the application header to this theming and
  sizing

Signed-off-by: Sebastian Kügler <sebas@kde.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-mobile/theme/Theme.qml

@@ -1,7 +1,10 @@
 import QtQuick 2.3
 
 QtObject {
+	property color accentColor: "#114d6f"
+	property color accentTextColor: "#ececec"
 	property color textColor: "#333333"
 	property color backgroundColor: "#ececec"
 	property color highlightColor: "#91c4e1"
+	property color highlightTextColor: "#333333"
 }

qt-mobile/theme/Units.qml

@@ -2,4 +2,5 @@ import QtQuick 2.3
 
 QtObject {
 	property int gridUnit: 24
+	property int spacing: gridUnit / 3
 }