Fix CatShards tests

Previously asserting that Node or Docs were not null or empty, but this
isn't a valid test when unassigned shards exist in the cluster.  In this
case, the cat api will return an empty string.  Switched to test for state
which should always be present.
Fix FieldsTest: should not search all types

The Content field is being checked for, but only the elasticsearchprojects
type contains this field.  This was causing an ArgumentNullException.
Decouple ScrollTests from number of shards and docs
Skip GeoBounds agg test on ES versions <= 1.3
Skip percentile ranks and top hits tests on ES < 1.3