DATAJPA-606 - Improve handling of empty arrays and collections in query parameters.

Prepare issue branch.
DATAJPA-606 - Improve handling of empty arrays and collections in query parameters.

Introduced potentiallyConvertEmptyCollection method to PersistenceProvider for provider specific handling of empty collections. Special handling is performed for Hibernate and EclipseLink. Conversion is performed in ParameterMetadata.prepare(..). Renamed ParameterMetadataProvider.accessor to bindableParameterValues.

This is an version of the original pr: #123 adjusted to the 1.7.x branch.

Original pull request: #124.