Move AMF0 classes to new package and add basic codec association classes.

MOD Move AMF0 classes to new subpackage "v0" to organize AMF0 specific classes.
ADD NoCodecAssociationException for when there is no association between a Java type and an AMF type.
ADD AMF0CodecMapping to allow establishing associations between Java and AMF0 types.
MOD Move AMF0EncodingBuilderNGTest class to mirror the package move made by the tested AMF0EncodingBuilder class.
ADD Package level Javadoc for new packages.