Promosing work toward metadata driven filter branches. A few methods
to construct them are stubbed out; all the data types and pure code
seems good.
This commit was sponsored by Walter Somerville.
Adds metadata log, and command.
Note that unsetting field values seems to currently be broken.
And in general this has had all of 2 minutes worth of testing.
This commit was sponsored by Julien Lefrique.
A very haskell commit! Just data types, instances to serialize the metadata
to a nice format, and QuickCheck tests.
This commit was sponsored by Andreas Leha.