Add additional fields per v0.2 of HSDS

This is the first of a series of pull requests that will attempt to match v0.2 of HSDS as closely as possible, except where ambiguity exists. I have been commenting on the spec here: https://docs.google.com/a/codeforamerica.org/document/d/1RH89UY7FDndivWNmtQkql4tdRTwYnCZluyu8itp5nTw/edit

**Fields added to the Organizations table:**

- alternate_name
- date_incorporated
- description
- email
- legal_status
- tax_id
- tax_status
- website

The `urls` field has been removed because it has been replaced by the
singular `website` field.

All of the new fields are exposed by the API except `legal_status`,
`tax_status`, and `tax_id`.

All of the new fields can be updated or added to a new organization via
the admin interface or via writing to the API.

The description field is required per the OpenReferral spec.

The following fields defined in the spec have not been added because
it’s not clear whether or not they belong in the Organizations table or
the Locations table:

- license
- accreditation
- funding

**Fields added to the Locations table:**

- alternate_name
- virtual

**Fields added to the Address table:**
- street_2
- country_code (required)
- renamed `street` to `street_1`
- renamed `zip` to `postal_code`

**Fields added to the MailAddress table:**
- street_2
- country_code (required)
- renamed `street` to `street_1`
- renamed `zip` to `postal_code`

**Fields changed/added to the Contacts table:**
- added `department`
- removed: `phone`, `extension`, `fax`
Instead of defining fax and phone numbers as Contact attributes, they are now associated to the Contact via the Phones table.

**Changes to the Phones table**
The `number_type` field, which is now required, accepts one of four
values:
- fax
- hotline
- tty
- voice

The optional `country_prefix` field has been added to the Phones table.
Valid values are country dialing codes, including the `+`, such as
`+212` for Morocco.

**Dropped the Faxes table**
Instead of having a separate table for Faxes, we can use the
`number_type` field in the Phones table to identify a fax.