Basic User Login Functionality

[atra2396]

Nothing super advanced, subject to changes later of course. Wanted just enough that the frontend could take this and run with it. Changes as follows:

• Added a User entity, a new controller for user account management - namely, account creation and login.
• Login will drop a JWT cookie into the caller's browser which is used to authenticate with the rest of the endpoints.
• Passwords are salted, encrypted, and stored in the db.
• The JWT key, password key, and password salt are all stored in the API's appconfig. A dummy app config has been provided for testing.
• Been on an integration test kick, so I added a couple. They test creating an account, logging in, getting back a valid token, and also creating an account and then failing to log in.

What this PR does not do:

• No connection from users to organizations
• No "admin" users
• No refresh tokens
• No "forgot password" functionality

[atra2396]

@eurubkov Would you like to take a look at this for me?

[eurubkov]

@atra2396 Looks fine to me