Reduce overhead in meta scans

Change scan_base, so that meta scripts only need to call init once and then just call start, not reinitializing all links before every scan

mentioned in issue #110 (closed)

mentioned in issue #121 (closed)

mentioned in merge request !176 (merged)

mentioned in issue #226 (closed)

removed milestone

assigned to @dphol and unassigned @mdaas

mentioned in merge request !250 (merged)

mentioned in merge request !255 (merged)

mentioned in commit 98c70d47

closed via merge request !255 (merged)