Added a first small set of hamcrest matchers

A first implementation of adding matchers and helper methods to elasticsearch.
The following ones are supported

assertHitCount(searchResponse, 2);

// helper methods to easily access the first hits
assertFirstHit(searchResponse, hasId("foo")):
assertSecondHit(searchResponse, hasType("foo")):
assertThirdHit(searchResponse, hasIndex("foo")):

// methods to access all other hits
assertSearchHit(searchResponse, 5, hasId("10"));
// same as above, but maybe more readable
assertSearchHit(searchResponse.getHits().getAt(5), hasIndex("foo"));

I changed GeoFilterTests to show how it works.

Furthermore I inlined assertHighlight() from HighlighterSearchTests.
The ElasticsearchAssertions class can be used now as a centralized assertion class
in order have a centralized class for every developer to look at.
Introduced a Opertaion enum that is passed to each call of
WeightFunction#weight to allow dedicated weight calculations per operation. In certain
circumstance it is more efficient / required to ignore certain factors in the weight
calculation to prevent for instance relocations if they are solely triggered by tie-breakers.
In particular the primary balance property should not be taken into account if the delta for
early termination is calculated since otherwise a relocation could be triggered solely by the
fact that two nodes have different amount of primaries allocated to them.

Closes #2984
Improve stability of SimpleDataNodesTests

Make sure that we are waiting for the new state to be propagated to the node where we are executing the followup query that depends on this state.