Refresh of the FreeMarker Component

I've made a number of small changes to the FreeMarker component:

• General re-format
• Added constants for the "encoding" and "contentCache" parameters
• Removed the unused FREEMARKER_RESOURCE constant
• Removed the unnecessary "FREEMARKER_" prefix of the FREEMARKER_RESOURCE_URI and FREEMARKER_TEMPLATE constants
• Removed the unnecessary getExchangePattern method
• Replaced the NoCacheStorage class by a call to a constructor of the Template class, that doesn't use any cache
• Added a default value for the "encoding" parameter (the platform's default)
• Added a specific exception class to support global exception handlers
• Renamed all classes from Free*m*arker (wrong) to Free*M*arker
• Renamed properties from CamelFree*m*arkerResourceUri (wrong) to CamelFree*M*arkerResourceUri and CamelFree*m*arkerTemplate to CamelFree*M*arker
• Replaced isDebugEnabled by log.debug as per CAMEL-3759
• Improved log messages

All tests run successfully.