Support for deep property names (without changing IElasticMapping).
Convert IElasticMapping to use MemberExpression instead of MemberInfo.
Fix remaining unit tests from deep query work.
Merge branch 'dev-deepquery-elasticmapping' into dev

Conflicts:
	Source/ElasticLINQ.Test/Mapping/ElasticFieldsMappingWrapperTests.cs
	Source/ElasticLINQ/Mapping/IElasticMapping.cs