E-mail sever only login once & UiO server settings.

Rewriting of the e-mail server login / out structure.  Additiation is
new class `SMTPUiO` and `SMTPGoogle` which are both subclasses of email
server class meant for for holding e-mail server connection which must
be given when initializing an `Email` instance.  This also gives
functionality for sending from a UiO e-mail address. New command-line
argument `smtp` lets user choose which server. UiO server takes both
e-mail adress for e-mail envelope and username for logging in.

This solves problem where server had to keep logging in / out for each
e-mail sent.