implements #1083 Get Index Api
Merge branch 'develop' into feature/get-index

Conflicts:
	src/CodeGeneration/CodeGeneration.LowLevelClient/ApiEndpoints/root.html
	src/Nest/IElasticClient.cs
	src/Nest/Nest.csproj
	src/Tests/Nest.Tests.Unit/BigBadUrlUnitTests.cs
added support for terminate_after elasticsearch/elasticsearch#6885
fix #1111 added support for significant terms heuristics elasticsearch/elasticsearch#6858
fix #1127 missing lang property on metricaggregationbase, also noticed it was missing updatedesciptor
Merge branch 'develop' of github.com:elasticsearch/elasticsearch-net into develop
fix #1113 add support to mpercolate and percolate highlighting
added missing constructors
Merge pull request #1119 from elasticsearch/feature/get-index

implements #1083 Get Index Api
Merge pull request #1130 from elasticsearch/feature/percolate-highlight

fix #1113 add support to mpercolate and percolate highlighting
Merge pull request #1129 from elasticsearch/feature/sig-terms-heuristics

fix #1111 added support for significant terms heuristics
Merge pull request #1128 from elasticsearch/feature/terminate-after

added support for terminate_after elasticsearch/elasticsearch#6885
Fix broken mapping test after #1104
fix #1134 ElasticContractResolver could use some else if action
Merge branch 'develop' into feature/aggs-scriptedmetric
fixed double implementation of language in develop and this branch causing the tests to fail