validate nested array values in INSERT and UPDATE statements
Merge pull request #1397 from crate/m/nested_arrays

validate nested array values in INSERT and UPDATE statements
fix NPE while handling shard failures of a distributed collect
Add sql query circuit breaker.

This adds a sql query circuit breaker which tries to estimate the amount of memory needed by a certain operation of a query to prevent a OutOfMemory exception.
It raises a CircuitBreakingException if the limit exceeded.
The default limit is 60% of the available HEAP.

The limit can be configured using the ``crate.breaker.query.limit`` and related ``crate.breaker.query.overhead`` settings.
fixup! Add sql query circuit breaker.