bulk refresh and update mapping cluster events
try and bulk as much as possible refresh and update mapping events, so they will all be processed at a single go, resulting in less cluster change events, and also reduce the load of multiple changes to the same index
also, change the prio for those to HIGH, since we want URGENT ones (like create index, delete index) to execute
better logging on failure to create index
if the index already exists, trace log it, since it might happen as a result of multiple index requests at the same time creating the index, all other ones, should be debug and not warn in the same spirit of other APIs
Added prefix suggestions based on AnalyzingSuggester

This commit introduces near realtime suggestions. For more information about
its usage refer to github issue #TODO

From the implementation point of view, a custom AnalyzingSuggester is used
in combination with a custom postingsformat (which is not exposed to the user
anywhere for him to use).