Implement stemming support

[GlennRicaud]

The purpose is to allow to index and search on properties using stemming. Choice made: Use existing algorithmic stemming proposed by ES.

• Add ES analyzers and mappings (search-settings.json and search-mappings.json) ._en, ._no, (All the languages available in ES: https://www.elastic.co/guide/en/elasticsearch/reference/2.4/analysis-stemmer-tokenfilter.html)

• Add a new field "language" on IndexConfig

• Adapt the Node API

  • We can already specify the index config. Handle the new field "language"

• Adapt Content layer. If there is a language set for the content, pass an additional IndexConfig for the property "_allText" with the appropriate language

• Create new query function: stemmed(fields, search-string, operator, language)

• Dump migration

  • Adapt existing IndexConfigs
  • For all contents, read language and set new IndexConfig

[GlennRicaud]

Useful links: ES reference: https://www.elastic.co/guide/en/elasticsearch/reference/2.4/index.html To enabled HTTP api of ES: Set http.enabled = true in com.enonic.xp.elasticsearch.cfg Example: http://localhost:9200/search-cms-repo/draft/_search?q=_id:features