PDB-249 Fix command-processing configuration exceptions

The use of (s/maybe s/Int) for the configuration options store-usage and
temp-usage were throwing exceptions when these configuration options were
used.

So this is really a bug in the convert-schema support, but in our case
we don't need to support the concept of 'nil' or 's/Int' for these items
(which is what s/maybe effectively does) since they are already marked as
optional.

This patch removes the use of s/maybe removing the exception, but does not
fix the original bug.

Signed-off-by: Ken Barber <ken@bob.sh>
PDB-249 Pass through values directly during get-construct-fn for core types

Previously for types schema.core.Predicate the function get-construct-fn was
failing as there was no support. This patch extends the PredicateConstructFn
protocol to support these types by simply passing through the value without
coercion or change.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #782 from kbarber/ticket/master/PDB-249_commands-config-exceptions

PDB-249 commands config exceptions