about half done with codec-jackson

- field config and pluggable should be working correctly
- type resolver is incomplete but no clear blockers
- not yet sure how to best integrate the global defaults logic
mostly functional at this point

= ended up just using the tree/ node api a lot to simulate the
kind of parsing CodecConfig et al did. The API support for doing
global defaults, required fields, et al just isn't really there
otherwise. Wasn't worth the myriad combinations of hacks and huge
time loss.

- couple known issues: enums need to be case insensitive, _rename
directives need to be respected, 'nested primaries' need to be
ported. The dropwizard size parsing i'm using is somewhat less
generous, so might need to rethink shimming back into typesafe.
fix enum casing
fix alias defaults for _default
fix implicit _primary object values

and some partial support for _primary paths for other cases
call getNullValue() less often; makes less garbage
use CodecBeanDeserializer as much as possible

previously was only doing so when a global default was found, but
it provides other features such as required fields, eliding nulls,
and Time/Bytes annotations. some of which may be possible to split
off, but we'll defer that for now.
add some codec json-like parsing options
support non-codec type mappings

should eventually be able to merge PluginMap with
CodecTypeIdResolver, but this more than suffices for now.
add jsr303 validation support
add some accessors in case they are useful
allow enums named after booleans + more jackson
more support for concrete creation of subtypes