BF: Resolve Deprecation Warnings for python3

Mainly python imp -> importlib for python3.3+, and other minor tweaks
Merge pull request #581 from kwirk/datetemplate-regroupdict

ENH: Full regex for datepattern, utilising modified Python `_strptime`
BF: Kerio log datepattern fix for recent datepattern full regex merge
TST+BF: Add tests for python actions, including test for smtp.py

Also fix bug when specifying multiple recipients for smtp.py action
BF: Tweak python action tests and fix Deprecation Warning