Add a schema module

[dnephin]

The current getters interface does not make it obvious that what you're getting is a ValueProxy. What you're really doing is defining a config schema for a class, which can be reloaded. A better (higher level) interface for this might be a more declarative approach:

@ConfigSchema
class SchemaA(object):

     namespace=  'the_namespace'
     path = 'something.A'

     field_a = ConfValue(Int, default=1)
     field_b = ConfValue(Float)

[dnephin]

A basic version of this has been added. If it proves to be useful, we can expand on it.