Create Profile and sync_leads: fix bug 1012904

Move choices from UserRegistrationLeadForm to Profile model
Create or update Profile in UserRegistrationLeadForm.save()
Use Rest API and sync updates to salesforce leads
So I made the mistake of going and writing the decorator just b/c I wanted to, then re-realized why I hadn't done it before: it doesn't actually save a single line, because applying the decorator itself takes the line you saved by eliminating the `sf = sf or None` from the function definition, and the decorator isn't particularly elegant, either:
```python
def sf_default(f):
    @wraps(f)
    def wrapper(*args, **kwargs):
        kwargs['sf'] = kwargs.get('sf') or Salesforce(**settings.SALESFORCE)
        return f(*args, **kwargs)
    return wrapper
```
So I'm back to leaving the code as is :/