Correct and improve javadoc comments in MatchAccumulator.
Fix formatting inconsistencies in the code for the examples.
Fix code formatting issues in main source code.
Move main code into new 'core' package.
Remove dependence on SLF4J for consumers where logging is not required.

Logging is now optional. Extend CompositePropertyMatcher where logging is
not required. In this case SLF4J is not a required dependency. Where
logging is required, extend LoggingCompositePropertyMatcher -
there will then be a runtime dependency on SLF4J. Consumers can
instead write their own extension to CompositePropertyMatcher to use
alternative logging libraries.
Fix maven warning relating to character encoding.

Explicitly state that we are using UTF-8.