Move complete bootstrap process into freezing-model with script

[obscurerichard]

Right now the only place in the code that bootstraps the model is from the freezing.web init:

import os
import os.path

from flask import Flask, session, g
from freezing.model import init_model, meta

from .config import config

app = Flask(__name__, static_url_path='/assets')
app.config.from_object(config)

init_model(config.SQLALCHEMY_URL)

It would be good to have a freezing-model init command that would do this also, something that paid attention to the SQLALCHEMY_URL or a command line switch for the URL.

If we did it this, and packaged it into Docker, we could have the database upgrade process decoupled from the web initialization process. That would be beneficial in that a mistake in the database upgrade would not prevent the web site from starting.