[Backend] Process the keyword searching

[longnd]

Why

After the keyword file is uploaded and the terms are parsed, implement the searching for each keyword and extract the search results to save to DB.

Acceptance Criteria

• The search for each keyword must start to run as soon as they are parsed and save to DB.
• If the search fails to process, retry it after a certain time.
• Extract the following information from the search result and save in the DB:
  • Number of AdWords advertisers in the top position
  • Total number of AdWords advertisers on the page
  • URLs of the AdWords advertisers in the top position
  • Number of the non-AdWords results on the page
  • Total number of links (all of them) on the page
  • HTML code of the page/cache of the page.