Fixed svg typo in whitelist selector

After adding a not-in-whitelist warning, it turns out that svg was
getting filtered, because the selector query had a typo and was looking
for vg, not svg
Improving conventions, support rect

Added rect to whitelist, broke apart the whitelist selector string so
that it would be easier to maintain
Minor comments on bug
Comment cleanup
Don't detach detached elements

Also cleaned up some comments