rewrite five-point coeff matrix.
updated doc
update five-point license
Move non-CV functionality from core.hpp to separate utility.hpp header
Fixing segfault for near-zero-sized ellipses
repaired std::string handling
Merge pull request #681 from jbohren-forks:fix-ellipse-segfault
Merge pull request #657 from prclibo:master
Merge pull request #665 from taka-no-me:core_utility
Merge pull request #682 from vpisarev/python_str_fix

repaired std::string handling