Background color changable
Added color settings background (still some bugs)

Conflicts:
Code/ShoppingList/res/values/strings.xml
Code/ShoppingList/src/ch/unibe/ese/shopnote/core/BaseActivity.java
Background color changable (still some bugs)

Conflicts:
	Code/ShoppingList/res/values/strings.xml
	Code/ShoppingList/src/ch/unibe/ese/shopnote/core/BaseActivity.java