Disable/Enabling facets always results in a entirely new query

[Laurel1012]

instead we should:

• only query the missing part
• keep computed parts even if it is disabled (so we can show it again for free)

[Laurel1012]

phase 1: track state of each facet:

• active: {boolean} included in vis or not
• fetchState: {enum: {'no', 'requested', 'fetched'}:
• result: result table

phase 2: update vis instead of redrawing

• at least keep current zoom state, etc

[Laurel1012]

now implemented in facet_state branch