HSEARCH-968 Indexing Dates and Calendar instances numerically

Introducing a new option to @DateBridge and @CalendarBridge to determine encoding type
HSEARCH-1741 Various documentation improvements links and formatting enhancements
HSEARCH-1739 Rename SearchFactoryBuilder to SearchIntegratorBuilder
HSEARCH-1740 Prefer using SearchIntegrator over SearchFactoryImplementor wherever possible
HSEARCH-1740 Move SearchFactoryImplementor to a dedicated 'impl' package
HSEARCH-1730 Move all .impl classes in hibernate-search-engine into engine.impl
HSEARCH-1673 Move SearchMappingBuilder to be an SPI
HSEARCH-1673 InfinispanDirectoryProvider also promoted to SPI
HSEARCH-1673 Promote DirectoryBasedIndexManager to an SPI package
HSEARCH-1673 Expose the default SimpleInitializer reference to SPI without exposing the implementation class
Preparing release 5.0.0.CR1 : update README and changelog
[maven-release-plugin] prepare release 5.0.0.CR1
[maven-release-plugin] prepare for next development iteration
HSEARCH-1743 Rename SearchFactoryImplementor to ExtendedSearchIntegrator
HSEARCH-1744 Making sure NumericFieldBridge#objectToString can handle null values

Also making sure all builtin bridges have a default constructor which is a requirement for
the bridge being usuable via the @FieldBridge annotation.