Merge branch 'issue/388' into 'master'

app/controllers/v1/search_controller.rb

app/models/educational_stage.rb

app/models/object_type.rb

app/models/search.rb

app/models/subject.rb

app/models/tag.rb

app/models/user.rb

db/migrate/20190219142846_create_searches.rb

...igrate/20190225143721_create_join_table_search_subject.rb

...90226122727_create_join_table_educational_stage_search.rb

...te/20190226122759_create_join_table_object_type_search.rb

db/migrate/20190226131445_create_join_table_search_tag.rb

...0190313143808_add_number_of_results_column_to_searches.rb