Currently the query builders expose the clauses of the span
query as a modifiable list. Instead we should make the that
getter return an unmodifiable list. Also renaming the method
used to add a clause from `clause(spanQuery)` to
`addClause(spanQuery)`.
The `ip` field uses a binary representation internally. This breaks when
rendering sort values in search responses since elasticsearch tries to write a
binary byte[] as an utf8 json string. This commit extends the `DocValueFormat`
API in order to give fields a chance to choose how to render values.
Closes#6077
QueryBuilder has generics, but those are never used: all call sites use
`QueryBuilder<?>`. Only `AbstractQueryBuilder` needs generics so that the base
class can contain a default implementation for setters that returns `this`.
The available memory metric was always set to `0` since 2.0.beta1 (bug). was left behind but never set. Turns out the section wasn't that useful, as it would only output the total memory available throughout all nodes in the cluster. We decided to remove the section then.
