Semtype objects that override schema

[jtc42]

This would make the property builder a LOT more useful.

Some semantic types require extra schema info, for example: https://iot.mozilla.org/schemas/#LevelProperty
LevelProperty requires limits.

Rather than having semantic types as a string, instead pass an object, such as semantics.LevelProperty(0, 100) which would automatically set the field to int type, and set the field limits to 0-100.

[jtc42]

In decorator form, this would override the Schema decorator, for example:

@semantics.moz.LevelProperty(0, 100)
class MyLevelProperty(PropertyView):
   ...

would be equivalent to:

@PropertySchema(fields.Int(required=True, minimum=0, maximum=100)
@Semtype("LevelProperty")
class MyLevelProperty(PropertyView):
   ...

[jtc42]

Now out of scope