HR-200

create activity type : "Visa Expiration" - for this used hook_civicrm_install 

implemented CRM_HRVisa_Activity::sync($contactId) - as per issue description : 
 - this activity will consist 'Added By' as the <code>$contactId</code> being synced and activity_date_time as end date of latest visa immigration record and status value as stated in description. 
 - if 'is_visa_required' is not set for a contact, creation of 'Visa Expiration' activity (if there isn't already) will not take place.

NOTE : added comments of TODO: with proper action to perform on each hook, for invokation of schedule reminder API (yet to be implemented : http://issues.civicrm.org/jira/browse/CRM-13615).