Fixes #750: New Settings Screen

* before testing, backup your prefs. You can't go back to a version without the new preferences dialog. I had to migrate some preferences.
* The old settings dialog still exists. Just some texts are changed. This I will switch off when we are done discussing this PR.
* Info text for geocaching.com appears when gc.com is activated (checkbox). This is one possible approach.
* New: slider for waypoints threshold. values: 0 to 50
* Info text for offline maps and themes changed - now in popup dialog
* removed: submenu in old settings to reset login data. Either deactivate a service or remove password of GcVote
* titlebar: settings cannot be embedded in another layout (with cgeo titlebar). A good looking title bar comes with the usage of ActionBarSherlock
* preference headers (e.g. "standard navigation" in "More Settings"): I think these should be styled to be more distinguishable. The problem is all the other small text around some headers. It looks quite chaotic. But the small texts are necessary, I think.
* someone has to test it on a tablet. I absolutely don't know how that looks on a large screen. Can't test it, my laptop is too slow for some Android versions in the emulators
* screen rotation magically works out of the box
* how do I make 1 commit out of these 7 commits?