Closes #24 (closed)
Added a GraphAPI version to access the mails instead of IMAP protocol.
Graph is supposed to be better according to MS to access mails.
Token refresh process was also optimized.
ISSUE (on all versions): Since the move to 365, no more List-ID and Delivered-To headers.
EGroups cannot be detected anymore (so the feature 'send from egroup' is broken)
A mail sent to an egroup with a notification channel mail as member will fail to be injected, as the To will be the egroup, and no header contains the channel mail (was set in Delivered-To).
