Commenting, Login system change, Adding some fields.

Commenting: Add some comments in query.pl

Login system change: After login, the web will jump to previous
visiting page when possible, instead of coming back to ‘/‘ as the old
times.

Adding some fields: Based on CABRI standard, ‘Other_names’ added to
both ‘Plasmid’ and ‘Strain’ databases, and ‘Isolated_from’ and
‘Geographic_location’ added to ‘Strain’ database. In relation to this,
relevant templates were updated, too.