Minor wording adjustment (define -> declare)
HSEARCH-1578 Fix {Array|Iterable|Map}BridgeTest to properly use null tokens

When passing the null token value tot he DSL, the field bridge must be
disabled.
HSEARCH-1552 Simplify null marker handling and collection of simple types
HSEARCH-1552 Make more methods private in BridgeFactory
HSEARCH-1552 BridgeFactory - Factor out bridge creation in dedicated providers

- create BridgeProvider SPI
- create ExtendedProdgeProvider private interface with more powers
- extract date, calendar, tika, spatial, numeric, enum and basic JDK
  types into providers
HSEARCH-1552 Loop through defined provider and raises exception for duplicates
HSEARCH-1552 Add ServiceLoader lookup for custom BridgeProviders
HSEARCH-1552 Check validity of return type when the Tika bridge is built rather than at execution
HSEARCH-1552 Minor renaming and method moves around BridgeProvider

- rename BridgeProvider method to provideFieldBridge
- move getMemberName to ExtendedBridgeContext
HSEARCH-1552 Add documentation for BridgeProvider