`BatchPoints.Builder` not reusable

Nobody has claimed this yet.

There's nothing in `BatchPoints.Builder` javadoc that would warn against calling `build()` multiple times:
https://github.com/influxdata/influxdb-java/blob/b1d1d8a2ed4430f6b6ac271362acab7b493be984/src/main/java/org/influxdb/dto/BatchPoints.java#L54-L57
https://github.com/influxdata/influxdb-java/blob/b1d1d8a2ed4430f6b6ac271362acab7b493be984/src/main/java/org/influxdb/dto/BatchPoints.java#L151-L156

and nothing in `build()` method itself that would cause ie exception:
https://github.com/influxdata/influxdb-java/blob/b1d1d8a2ed4430f6b6ac271362acab7b493be984/src/main/java/org/influxdb/dto/BatchPoints.java#L156-L174

but creating multiple `BatchPoints` instances from `BatchPoints.Builder` is not actually safe since `BatchPoints.Builder` does not make defensive copy of `this.points`:
https://github.com/influxdata/influxdb-java/blob/b1d1d8a2ed4430f6b6ac271362acab7b493be984/src/main/java/org/influxdb/dto/BatchPoints.java#L162

so ie this code will fail:
```java
BatchPoints bp1 = builder.build();
int size = bp1.getPoints().size();
bp1.point(point);
BatchPoints bp2 = builder.build();
assertEquals(size, bp2.getPoints().size());
```
since `bp1.point(point)` modified collection `builder` refers to.

Start in src/main/java/org/influxdb/dto/BatchPoints.java, especially BatchPoints.Builder.build() and the points collection referenced around lines 156-174. Reproduce the issue with the two-build example from the report; done means separately built BatchPoints instances no longer share mutable point state.

Written by the indexing model from the issue text.