Fix area rendering: assign objectType=3 (polygon)

Seems that this rule does not assign objectType="3" to areas, because empty tags or values ("") do not work in this case?
> \<filter area="true" tag="" value="" order="5" objectType="3"/\>

So areas which should be rendered as areas have to be specified explicitly.

If I specify them explicitly (see patch), areas are rendered correctly.

https://groups.google.com/forum/#!topic/osmand/pfS_rR8w1ZY