Implement ability to set() struct and list fields by deep-copying from a corresponding Reader.  This copy requires no schema knowledge.

Restore ability to upgrade from List(Bool) to List(T) where T is a struct whose @0 field is of type Bool.  I previously disallowed this to reduce complexity, but it turned out to actually increase complexity.

Delete Code Friday:  Inline structs/lists/data are too complicated for not enough benefit.  There goes a week of my life that I'll never get back.

Correctly handle inline fields that aren't present in the parent struct (i.e. because we're reading an older version of the struct that lacked those fields).

Make enum syntax match docs, make enum lists work correctly, add enum tests, enforce maximum ordinals on enum values and interface methods, change the maximum field ordinal to 16-bit to match docs (now all ordinal limits match).

Rename the 'Message' interfaces to Arena and make them internal.  Make a new, intuitive 'Message' interface for creating / reading messages.

Basic code generation starting to work.  My machine just did something weird so I'm submitting and pushing in case of imminant hardware failure...