Add some rally scenarios

This change adds configuration directory for rally.

Implements blueprint rally-gate-check

Change-Id: I49ed3025bb90355b851526af9b5a469c7c84fdc9
Improve links in config docs

Currently duplication part from configuration.rst file was removed
(patch https://review.openstack.org/#/c/133035) but links in events.rst are
still refering to removed part of docs.

This patch improves links.

Closes-bug: #1401444
Change-Id: I99037f99f3fcb40eb27b56e1581bf60f32ff3051
Merge "Add some rally scenarios"
Merge "Improve links in config docs"