errorlib: register_emergency() sends email not SMS
- separated the fetching of the configuration from the actual sending, partly to allow for flexibility in calling, but also to allow for easier unit testing
- removed CFG_SITE_EMERGENCY_PHONE_NUMBERS and added CFG_SITE_EMERGENCY_EMAIL_ADDRESSES
- moved bibtask.parse_runtime_limit function into dateutils
- added tests for parse_runtime_limit
- added CFG_SITE_EMERGENCY_EMAIL_ADDRESSES setting to special 'dict' options in inveniocfg.py
- removed errorlib.send_sms function;
- modified errorlib.register_emergency to read CFG_SITE_EMERGENCY_EMAIL_ADDRESSES and call send_email depending on configured date/time constraints
- added test for errorlib.get_emergency_recipients
- closes #242