BoundingBox: rightDown() and leftUp() were added
BoundingBox: 'box' field is now protected, now private; Rectangle::getDistanceToBorder was implemented
Ellipse::getDistanceToBorder: some modifications to produce less warning on my 'not implemented yet' workaround
Some codestyle fixes
model.h: big getDistanceTo* methods were moved to *.cpp (#10)
model.h: a bit of code style fixes
Some tests for Segment::distanceToBorder were added