documentation

Pull request #4145: [DEV-4238] moved Aggregation in graphs content from standalone page to section within Graph, page deleted

Merge in WEB/documentation from feature/DEV-4238-7.5-D-s4 to release/8.0

* commit 'ecd8e2a6531b86b2aef3a7eac7b1869ada759afa':
  [DEV-4238] removed reference (sub-issue 4)
  [DEV-4238] updated description (sub-issue 4)
  [DEV-4238] deleted page after moving content
  [DEV-4238] updated image
  [DEV-4238] updated references
  [DEV-4238] added Aggregation in graphs section