[2.3] [Re-build] Manager Theme: Adjust appearance of saving window

This PR makes the saving progressbar fit better into the theme and stop using background images to save a few requests (not sure if the splash color is a good choice though, what is your opinion?)

before:
![bildschirmfoto 2014-07-21 um 15 17 56](https://cloud.githubusercontent.com/assets/445501/3644269/8ef9e152-10de-11e4-980c-40e81237854a.png)

after:
![bildschirmfoto 2014-07-21 um 15 50 52](https://cloud.githubusercontent.com/assets/445501/3644272/9366de84-10de-11e4-91dd-3d2ae05439db.png)