Bookmark Manager: fix bug of search mode conflicting with reordering
Bookmark Manager: fix bug of search mode conflicting with reordering

This bug was found by following steps:
1. Tap in "search bookmarks" to type in some characters to search
2. Clear search string to back to normal mode
3. Bookmark items will now fail to be reordered

This problem is caused by dynamic sort feature in QSortFilterProxyModel,
as we are not using this feature, so it is removed to fix this bug.

Reviewed by Junmin

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser