Better generated code

Improved format and structure of generated code.  Code that has moved
into the core library has been removed. Reduced the number of lines
generated dramatically while improving readability.
Small updates to initializers

Surprising the number of methods missed after the instancetype branch.
Instance method, defaultInstance moved to library

The instance version of defaultInstance, has moved into the support
library and does not need to be generated.  It now just forwards the
message to the class method implemented in each generated class.
Minor fixups to formatting
Merge branch 'gen-less-better-code'