Update API, Update Wallet

Emails can be linked to wallets. Close #19
Passwords can be changed. Close #7
set_option database calls now take a variable name instead of an id
Added in functionality for sending emails with a custom theme
Started on backend to allow for 2fa via authy. Currently only setup for
email
wallet_getinfo now returns the username and email
Added API calls for changing wallet passwords and emails and added in
API documentation
Fixed multiple typos in the API / API doc
Demo API calls in the doc now show the current version