Support new half_float and scaled_float field types

Elasticsearch added a couple of new numeric datatypes, which means we
need to update our type casting list to include them. Kibana should
see them as "numbers" so they work properly in searches and aggs.

Fixes #7782
Related elastic/elasticsearch#18887
Related elastic/elasticsearch#19264

src/ui/public/index_patterns/_cast_mapping_type.js

@@ -12,6 +12,8 @@ export default function CastMappingTypeFn() {
       { name: 'date',         type: 'date',       group: 'base'   },
       { name: 'boolean',      type: 'boolean',    group: 'base'   },
       { name: 'float',        type: 'number',     group: 'number' },
+      { name: 'half_float',   type: 'number',     group: 'number' },
+      { name: 'scaled_float', type: 'number',     group: 'number' },
       { name: 'double',       type: 'number',     group: 'number' },
       { name: 'integer',      type: 'number',     group: 'number' },
       { name: 'long',         type: 'number',     group: 'number' },