Add a simpler <outline2> tag for custom maps

[jidanni]

On
http://www.offline-maps.net/en/help/map ... ed_example
<outline>2.54,49.49 2.54,51.51 6.41,51.51 6.41,49.49</outline>

Perhaps also allow a two points on the opposite sides of a rectangle
version,

<outline2>2.54,49.49 6.41,51.51</outline2>

like one can get from
http://tools.geofabrik.de/calc/#type=ge ... 5775&tab=2

[Psyberia-Support]

Or you can use this website: http://www.birdtheme.org/useful/v3tool.html
Just draw the area and take the coordinates from the generated "<coordinates>" tag.
This way you can draw any shapes, not only rectangles...