Move reset calls from *Bind methods to Next method.
It fixes the case when the previous step return an error.
But this will cause regression when a statement is not stepped until done.

xFunc and xStep must be split.

Add IntegrityCheck helper.

Add ExecInsert method to ease the use of autoincremented field.

Renamed NamedScanColumn to ScanByName.
Refactored BindParamaterIndex and BindParamaterName to return error on invalid param.
Added NamedBind.