CRM-12935 Added Job oriented fields, metrics and groupings

1. Added job fields,filters in summary & detail reports and group bys in summary report.
2. Calculated the Full Time Equivalents, Annual Cost Equivalents and Monthly Cost Equivalents based on the description given in http://wiki.civicrm.org/confluence/display/CRM/CiviHR+Report+Template. 

a) For Full Time Equivalents, I calculated it by taking the sum of hours_amount column of civicrm_hrjob_hour table for different job positions of a contact and dividing the sum by 40.
b) For Annual Cost Equivalents, I calculated it by taking the sum of pay_amount column of civicrm_hrjob_pay table for different job positions of a contact. 
c) Then for calculating Monthly Cost Equivalents, divided the sum obtained in step (b) by 12.