Multiple sending accounts

[mishaturnbull]

Feature planned for 2.x. Multiple accounts should be used as follows:

Amount  : 200
Sender  : ex1@example.com, ex2@example.com
Password: ex1pass, ex2pass

Amount will be evenly divided between accounts. If it does not divide evenly, raise a ValueError.
Sender and Password must be separated by , (commaspace). More accounts are allowed than passwords:

Amount  : 300
Sender  : ex1@example.com, ex2@example.com, ex3@example.com
Password: pass-for-ex1, pass-for-other-2

In this case, autofill the rest of the account details with the last password in the list.