utils: improve csv parser

harder: more const
better: allow \" and "" inside quoted fields
faster: will not eat MBs inside a string if the input is buggy
stronger: strong to exceptions thanks to std::unique_ptr

fix http://jira.canaltp.fr/browse/NAVITIAII-1360
Merge pull request #740 from TeXitoi/improve-csv-parser

utils: improve csv parser