[docs] Need to update OSTF contributor`s guide with information on OSTF profiles

[Anastasiia Naboikina]

It is necessary to describe what fields are mandatory in OSTF profiles and provide general information on how they work.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/84688

[Mike Scherbakov (mihgen)]

It doesn't need to be merged into stable/4.1, as we have only one version of Development Documentation deployed: docs.mirantis.com/fuel-dev, which is always build out of master branch.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/84688
Committed: https://git.openstack.org/cgit/stackforge/fuel-web/commit/?id=d593b43f0219447ca8d1434ee69265ab80a5e24f
Submitter: Jenkins
Branch: master

commit d593b43f0219447ca8d1434ee69265ab80a5e24f
Author: Anastasiia Naboikina <email address hidden>
Date: Wed Apr 2 13:23:30 2014 +0300

    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