Expose Node degree in REST API.
Replace 204 response with empty map for get empty properties, fixes #83.

- This makes client-side code slightly simpler, since it removes an edge case
  entirely - just return an empty map for empty properties.
- The 204 response was undocumented, so this does not break documented
  behavior.
- Remove duplicate integration tests, replace with simple full-stack test.
Fixes #3017

Changes behaviour for the simple CASE so that null as comparator results in the else expression being used
Merge pull request #3445 from petraselmer/null-case

Fixes #3017
Revert "Merge pull request #3445 from petraselmer/null-case"

This reverts commit ca1dde385209043ac25ab65fbe4ee2072385c83f, reversing
changes made to 3d722bc57520c498d62bf24e6074f023eb4824af.
Removed cardinality model for assuming dependent predicate selectivities
Updated cardinality estimation in the RHS of Apply to take LHS input cardinality from LogicalPlanningContext

On the side:

o Distinct is now 0.95 of input
o Other aggregations still are sqrt(input)
o Made sure QueryGraphs in sub queries have correct argument ids set
Introduce QueryGraphCardinalityInput into LogicalPlanningContext
Fix SchemaRuleCommand parser for 2.1
Test index counts are built correctly when migrating from 2.1 and 2.0
Remove BYTES_AS_INT use BYTES with proper min and max constraints instead
Add a test to make sure counts are propagated correctly in HA
Create a package for CountsKey and friends

- introduce a Factory for creating CountsKey
- make CountsKey to be an interface rather than an abstract class
Unify API on CountsStore to always use registers

- add a 'satisfies' method to the CopyableDoubleLongRegister to simplify assertions
Tweaks for import tools docs.
Keep label information when planning optional matches
Make all Metrics types use QueryGraphCardinalityInput
Merge pull request #3463 from systay/apply-cardinality

Apply cardinality
Merge pull request #3416 from davidegrohmann/2.2-migrate-counts-it

More tests and code cleanup related to IndexSelectivity
Merge pull request #3406 from jakewins/2.1-rest-degree

Expose Node degree in REST API.