change in ad parsing

[cqx931]

A few tweaks in ad parsing trying to fix many failing cases in ad collection.
Changes:

• Ad parsing in bootstrapPhase2() instead of bootstrapPhase1(), because many doms may still not loaded in bootstrapPhase1
• No children checking for HTML and BODY tags, as we don't want to scan the whole webpage for advertisements
• Remove duplicate ad check in domFilterer.commit()