Fix bridges

fix problems in bridge code
test files are here: https://drive.google.com/folderview?id=0B9HM4UOKDQBLNnREUkd4aDl2dzQ&usp=sharing

Without this, 3-support bridge direction is ignored (negative return value from bridge detector), bridge direction is 90ded off and infill is rotated in wrong direction if model is rotated (--rotate 10 passed to slic3r)