Fix/centroid

Fix for Geometries containing big coordinates values.

During the calculation of a centroid the strategy may perform calculus using great values, e.g. add squares of coordinates, which greately increases the numerical error. This is related with https://github.com/boostorg/geometry/pull/154.

The main idea is to move the Geometry closer to 0 and calculate the centroid for such Geometry. The new origin is the first Point of a Geometry. The translation is done on-the-fly as centroid is calculated. Then the resulting point is translated back.

The picture below shows the Polygon placed closer to 0 and further, plus their centroids before and after the fix.

![text3152](https://cloud.githubusercontent.com/assets/1226951/4600161/6b8980e8-50cf-11e4-8b71-67eac62defb0.png)

Apparently we have a new convention here, aligning new lines with the brackets before. AFAIR there is nothing in the guidelines about this.
I'm not against this, but please do not mix this (in the future) with bugfixes or other enhancements. Maybe we should discuss this on the list. If we do this, I'm in favour of putting all parameters separately, one per line