Make SimpleNodeSampler populate the list of connected nodes using the information returned from the cluster

This is to allow people to introspect things like data settings and attributes. Also makes it consistent with the sniff sampler.

Closes #4162
Fix file handle leak in URLBlobContainer
Fix possible race condition during snapshot deletion
remove deprecated method usage with jackson
Include inner classes in the test package as well
move bloom filter class to a more common package
multi_match query supports fields as single string and array

The multi_match query accepted only an array in the fields parameter. This patch allows to use a single string as well.

Also added tests for parsing in both cases.

Closes #4164