Change: start moving filter section out of manage_sql.c

[mattmundell]

What

Move first four functions from manage_sql.c to dedicated files.

Why

Better organisation. Smaller manage_sql.c.

References

Similar to #2523 for Assets.

Testing

• manage_filter_controls check start,max
  o m m '<get_targets filter="rows=5"/>'
o m m '<get_targets filter="first=2 rows=2"/>'
• manage_report_filter_controls check PORTS/COUNT, and manage_clean_filter check that min_qod added to FILTER/TERM
  o m m '<get_reports report_id="ce802cc5-d8ed-4f7f-b303-96cb0eed08da" details="1" filter="rows=3" report_filter="rows=4"/>'
• manage_clean_filter_remove check term reordering to confirm that it ran
  o m m '<get_targets filter_replace="xxx" filter="rows=1 xxx=33"/>'
  o m m '<get_targets filter="rows=1 xxx=33"/>'