FloatDocValues does not return true for 0 >< 1 values [LUCENE-4800]

The following function query should always yield 1 if the document's field matchers the query:

```Java
if(query({!lucene df=FIELD v=$q},0),1,0)
```

This is, however, not true if due to low IDF the score end up below 1 but, obviously, above 0. The if() statement does not recognize a number between zero and one as positive and therefore TRUE.

---
Migrated from [LUCENE-4800](https://issues.apache.org/jira/browse/LUCENE-4800) by Markus Jelsma, updated May 09 2016
Environment:
```
5.0-SNAPSHOT 1427825:1444730M - markus - 2013-02-11 11:39:54
```

Attachments: [LUCENE-4800-trunk.patch](https://apache.github.io/lucene-jira-archive/attachments/LUCENE-4800/LUCENE-4800-trunk.patch)

Start by locating the FloatDocValues implementation and the function-query evaluation path described in the issue. Reproduce the query with a score between zero and one, then verify that a matching document is treated as true and add or update coverage for that case.

Written by the indexing model from the issue text.