Remove superflous (and possibly dangerous) raise statement

[lbeltrame]

When vcf2db hits an exception when inserting multiple records at a time, it catches it then inserts single records, and if an exception occurs, prints the record as bad before raising the exception itself.

However, there are cases where the batch insertion fails, and the individual insertions succeed. In this case the code hits a second raise statement and interrupts loading, even though no error has occurred.

This commit removes the raise statement for these reasons:

• If an exception occurs and there is a bad record, the code will catch it anyway;
• If an exception does not occur, execution can continue instead of interrupting loading.

Note that this is a workaround more than a fix, since it is unclear why adding record in batch would fail, while individual records would work.

Workarounds issue #59.

[lbeltrame]

Dropping this. I wrote something to replace vcf2db internally which is not as full of problems.