Polylx

* bugfix

* added plots module (initial)
* representative_point for Grains implemented
* moments calculation including holes
* surfor and parror functions added
* orientation of polygons is unified and checked
* minbox shape method added

* shell script ipolylx opens interactive console

* Added MAEE (minimum area enclosing ellipse) to grain shape methods
* Removed embedded IPython and IPython requirements

* IPython added to requirements

* Sample has pairs property(dictionary) to map boundary id to grains id
* Sample triplets method returns list of grains id creating triple points