Added converter classes.
Fixed logback-access sandbox.
Added inheritance support to ConverterRegistry.
Implemented ConvertingStreamEventProducer and ConvertingServerSocketEventSourceProducer using ConverterRegistry.
Implemented log4j converter.
Implemented Logback access converter.
Implemented Logback classic converters.
Using Converter interface instead of derived class.
Using ConvertingSSESP instead of specific implementations.
Getting rid of producer-classic and producer-access modules.
Adding data-converter dependencies.
Refactoring module names and artifact ids.

:logback-access-adapter => :logback-converter-access
access-adapter => converter-access
de.huxhorn.lilith.logback.access-adapter => de.huxhorn.lilith.logback.converter-access

:logback-logging-adapter => :logback-converter-classic
logging-adapter => converter-classic
de.huxhorn.lilith.logback.logging-adapter => de.huxhorn.lilith.logback.converter-classic

:log4j-producer => :converter-log4j
log4j-producer => converter-log4j
de.huxhorn.lilith.log4j.producer => de.huxhorn.lilith.log4j.converter
Removed unused imports.
Fixed display name.