Merge branch 'transcription-search' into 'master'

src/arkindex/api_v1.py

src/documents/admin.py

src/documents/api.py

src/documents/importer.py

src/documents/management/commands/reindex.py

src/documents/managers.py

src/documents/migrations/0013_auto_20180502_0852.py

src/documents/migrations/0014_auto_20180502_0852.py

src/documents/migrations/0015_auto_20180502_0852.py

src/documents/models.py

src/documents/search.py

src/documents/serializers.py

src/documents/tests.py

src/images/importer.py

src/images/models.py