ISPN-4966 The <backups/> element should be a sub-element of all cache-types, not just clustered caches
Update locking documentation

* added how it works in clustered caches
ISPN-4970 AvailabilityException and AvailabilityMode are in the wrong package
ISPN-4970 AvailabilityException and AvailabilityMode are in the wrong package

Move the impl package as well
ISPN-4981 Update to Hibernate Search 5.0.0.Beta2
ISPN-4981 Spatial Query updated API: onCoordinates -> onField
ISPN-4902 Unsupported Class Version Error when running testsuite with JDK6

Update documentation.
ISPN-4950 Add ability to merge defaults into Metadata passed as param

* This is required in order to be able to apply default lifespan and
max idle settings configured globally for the cache.
* To do so, a new method has been added to builder that allows a
Metadata object to be merged with the builder instance.
* By making the default metadata builder implementation use objects
for primitives, it can easily distinguish between those settings
that have been set by the user versus the builder defaults.