Image query with vector two

[agnesgaroux]

• Reverts the reverted colour search changes
• Fixes rounding issue when creating colour filter queryVector
• Adds test combining query and knn colour search
  not sure it's in the right place
  please check whether the expected results for combines free test query and knn search in search/src/test/scala/weco/api/search/images/ImagesFiltersTest.scala is what we actually want:
  blue foot and pretty blue foot come first,
  3rd is the red foot because it's a closer match for foot even though it's not blue
  4th in line is less foot but more blue, and come after the red foot because foot takes precedence
  5th is no foot but it's blue
  6th is not foot nor blue