Specialise the default codec to reuse Lucene41 files in the common case.

Closes #2799
Lazily initialize the delegate in BloomFilteredPostingsFormat to prevent unnecessary loading if bloomfilter terminates early
# GeoShape Precision

The `geo_shape` precision could be only set via `tree_levels` so far. A new option `precision` now allows to set the levels of the underlying tree structures to be set by distances like `50m`. The def

## Example
```json
curl -XPUT 'http://127.0.0.1:9200/myindex/' -d '{
  "mappings" : {
      "type1": {
          "dynamic": "false",
          "properties": {
              "location" : {
                  "type" : "geo_shape",
                  "geohash" : "true",
                  "store" : "yes",
                  "precision":"50m"
              }
          }
      }
  }
}'
```

## Changes
- GeoUtils defines the [WGS84](http://en.wikipedia.org/wiki/WGS84) reference ellipsoid of earth
- DistanceUnits refer to a more precise definition of earth circumference
- DistanceUnits for inch, yard and meter have been defined
- Set default levels in GeoShapeFieldMapper to 50m precision

Closes #2803
release 0.90.0.RC1
move to 0.90.0.RC2 snap
Use more efficient StemmerOverrideFilter from Lucene trunk

Closes #2800