Fix issues in HTML views and API documentation

See #375. Deployed to staging: http://staging.api.lobid.org

Update item and subject sample queries in API documentation:

http://staging.api.lobid.org/item?id=BT000000079:DE-Sol1:GA+644
http://staging.api.lobid.org/subject?q=de

Fix missing HTML entries for multiple items and subjects:

http://staging.api.lobid.org/resource?id=HT004683464
http://staging.api.lobid.org/resource?id=HT015972673

Add `AllowEncodedSlashes On` to Apache config to fix some item queries:

http://lobid.org/item/HT004683464%3ADE-5%3A4%27+62%2F509