Add annotations to document()

[thisfred]

If teleport supports it, add information about additional restrictions to the documented schemas. (if not, provide a different way to show them.

For instance, something like:

def non_negative(value):
    """Must be >= 0."""
    return value >= 0

schema = Schema({
    "balance": And(int, non_negative)})

print(document(schema, with_annotations=True))
{"Struct": {
    "required": {"balance": "Integer"},
    "optional": {}}
 "[whatever teleport supports for this, if anything]": {
    "restrictions": {
        "balance": "Must be >= 0."}}}