Minor fix-ups on field definitions; fix kind of buildoutputs()

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extra : rebase_source : 3086e06c9ae020dfeee130d27c4481f543fafaa8
Add api.addAliases helper; allow field name arguments to api.unregister()

--HG--
extra : rebase_source : 6e5e2b6d20cb68e0525d310ade84736092240012