Allow limiting length of document ID
Previously it was not possibly to define a maxum document ID size. That meant
large document ID would hit various limitations and corner cases. For example,
large document IDs could be inserted via a _bulk_docs endpoint but then trying
to insert the same document via a single HTTP method like PUT would fail
because of a limitation in Mochiweb's HTTP parser.
Let operators specify a maxium document ID length via the
```
couchdb.max_document_id_length = infinity | Integer
```
configuration.
The default value of `infinity` keeps the current behavior where document
ID length is not checked.
COUCHDB-3293
3 files changed
