Quick Values improvements

[lennartkoopmann]

• Allow to sort on value, percentage or count
• Allow to build a chart of the values over time. This is important to see how values changed over time. This needs a "Only chart top 10[/30/100] values" to avoid huge charts with too many lines.
• Stacking of data based on another field. For example, you could run a quick values analysis on
  a source address field and then select to stack a source address against a destination address. This would then give you the top destination addresses the specific source IP has been talking to. You
  could also run this without selecting a source IP first and get all conversation pairs, together with their count.

Open Tasks

• Disable stacked field form if Elasticsearch is < 5.x
• Split stacked terms result into key value pairs to fix Quick Values widget: "Add to search query button" has wrong behavior #4216
  • Use WORD SEPARATOR MIDDLE DOT unicode character to join and split the stacked fields (but also make the character configurable)

[edmundoa]

Points 1 and 3 are implemented in #4205