improve input validation for objects and object arrays
fix cherry-pick issue
improve error message if num columns doesn't match number of values on insert
implemented node network stats
Merge pull request #923 from crate/m/network_stats_impl

implemented node network stats
documentation for node load metrics
Merge pull request #922 from crate/h/load-metrics-docs

documentation for node load metrics
os column wip
os expression on sys.nodes
fixup! os expression on sys.nodes