PolyLabel calculations

[devemux86]

PolyLabel sometimes produces labels at wrong places.
(see screenshot with polygon building labels in red)

Similarly to mapsforge/mapsforge#972 or mapsforge/mapsforge#930 for map-writer, the calculations can be intense for dense areas, leading to reduced performance.
So better revert to default implementation and provide PolyLabel via a flag, until it's further improved.

Parameters.POLY_LABEL = true;