Do we want to support a boolean return value for @Query("UPDATE... ?

Currently the Query Javadoc requires void, int, or long.

A TCK test was testing a boolean return type, but is being changed in #924 as the resolution to challenge #923 because the Javadoc does not currently permit boolean.

`boolean` would be trivial to implement, with true corresponding to a numeric result > 0, and false corresponding to a numeric result of 0.

`boolean` could be convenient when writing an DELETE or UPDATE statement (such as the one in the TCK) where there can be at most 1 matching entity, often due to querying based on the Id.

I'm fine with adding `boolean`, but the spec is also okay without it.

Start with the Query Javadoc and the TCK test mentioned in the issue, then review the related resolutions in #923 and #924. The work is not ready to begin until the project decides whether boolean return values should be supported; done would require the corresponding specification and test changes.

Written by the indexing model from the issue text.