[x] Change KDbSqlResult* KDbConnection::executeSQL to QSharedPointer<KDbSqlResult> KDbConnection::prepareSql (fixes risks of memory leaks and unfinished execution when resulting object is ignored)
[x] Change bool KDbConnection::executeVoidSQL to bool KDbConnection::executeSql (also in Kexi)
[x] Change KDbConnection::insertRecord to return QSharedPointer<KDbSqlResult> (fixes risks of memory leaks and unfinished execution when resulting object is ignored)
[x] Replace KDbConnection::executeSQL uses (also in Kexi) with KDbConnection::executeSql where needed (fix memory leak and unfinished execution)