Remove 'term_index_interval' and 'term_index_divisor'

These settings are no longer relevant since they are codec /
postingsformat level settings since Lucene 4.0

Closes #3912
Fix bug in explain for function_score queries.

The explain output for function_score queries with score_mode=max or
score_mode=min was incorrect, returning instead the value of the last
function.  This change fixes this.
moved log statements
Preference only_node with unknown nodeId returns useful exception

When the search preference is set to only node, but this node is not a
data (or does not exist), we return a search exception, which indicates,
that this is actually a server problem.

However specifying a non-existing node id is a client problem
and should return a more useful error message than
{"error":"SearchPhaseExecutionException[Failed to execute phase [query_fetch], all shards failed]","status":503}