Require minimum OTP R14, to fix compilation on OTP 17.
Add esqlite3:changes/3 function to get nr of affected rows
Return SQLITE_CONSTRAINT error
Pass back errors in fetch steps to the caller

Constraint errors (e.g. foreign keys) can fail in the fetch phase of a
query. The library did not support error handling in the fetch phase yet.
merge
Merge branch 'arjan-master'