Adding current metrics definitions for gitlab.com
@broyer1 - as agreed, I am incorporating on this page for now, but we will move it out of the finance portion of the handbook.
@ebrinkman - these are the current definitions. There are inconsistencies w.r.t how metrics are defined, so if everyone agrees, we can change the numbers and will amend to the correct definitions accordingly.
Edited by Virjinia Alexieva