Update delete-samples command to take multiple ids

Fix #261.

The ids are simply arguments after the command, each separated by a space. For example, if we wanted to delete samples with IDs 4 though 8 we could do:

`./bin/manage.py samples delete-sample 4 5 6 7 8`

Signed-off-by: Don Naegely <naegelyd@gmail.com>