After a new invitation is made on a resubmission the
reinvited referee will receive an additional mail
to notify him/her about the resubmission and his new invitation.

Also, explicitly added the host to links in the new mail templates
to prevent invalid links.

All required actions are determined and saved in `submission.cycle`
now. The actions required are determined at initialization of
the submission. Different cycles now possibly can have different required
actions. All template logic to determine required actions is removed
from the codebase.