Add description of profiles to OSTF Contributor`s Guide
Add description of profiles to OSTF Contributor`s Guide

Added description on how to use __profile__ dictionary
for setup of test sets.

Change-Id: I5da19861793928a98f602f11e6a13232e8ec1302
Closes-Bug: #1301286

zhaochao/fuel-web,zhaochao/fuel-web,huntxu/fuel-web,koder-ua/nailgun-fcert,nebril/fuel-web,zhaochao/fuel-web,prmtl/fuel-web,eayunstack/fuel-web,eayunstack/fuel-web,SmartInfrastructures/fuel-web-dev,koder-ua/nailgun-fcert,nebril/fuel-web,stackforge/fuel-web,eayunstack/fuel-web,prmtl/fuel-web,SmartInfrastructures/fuel-web-dev,nebril/fuel-web,huntxu/fuel-web,stackforge/fuel-web,eayunstack/fuel-web,koder-ua/nailgun-fcert,huntxu/fuel-web,SmartInfrastructures/fuel-web-dev,zhaochao/fuel-web,prmtl/fuel-web,stackforge/fuel-web,nebril/fuel-web,prmtl/fuel-web,koder-ua/nailgun-fcert,huntxu/fuel-web,prmtl/fuel-web,SmartInfrastructures/fuel-web-dev,huntxu/fuel-web,SmartInfrastructures/fuel-web-dev,nebril/fuel-web,eayunstack/fuel-web,zhaochao/fuel-web