add multi fields mapping

http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/mapping-core-types.html#_multi_fields_3
add global aggregation
add nested aggregation
Merge pull request #232 from vbehar/features/aggs_nested

add nested aggregation
Merge pull request #231 from vbehar/features/aggs_global

add global aggregation
Merge pull request #230 from vbehar/features/mapping_multi_fields

add multi fields mapping
Merge pull request #228 from hfgiii/master

added script fields functionality to SearchDsl
Tweaked script DSL. Added tests for scripts.
Update search.md
Updated some syntax to use case objects
Lovingly reformatted by scalariform
Added some new operations to count dsl
Added missing operations on optimize
Added missing operations to get dsl
Added missing operations to mlt
Added missing operations to explain dsl
Updated more def keywords to case objects
Fixed options error
Removed deprecated since 1.0.1.1method
Added missing version op to update dsl