Tidy up scheduler_evolution.rst
Tidy up scheduler_evolution.rst

This is primarily a writing style cleanup with some clarifications
and link additions. It does not make any great effort to bring the
information up to date with current conditions.

Change-Id: I665dc5afc952cf93c095cdd1421b64d7b0716b2a

cyx1231st/nova,sebrandon1/nova,cernops/nova,rahulunair/nova,klmitch/nova,dims/nova,Juniper/nova,alaski/nova,jianghuaw/nova,rajalokan/nova,vmturbo/nova,cloudbase/nova,Juniper/nova,klmitch/nova,gooddata/openstack-nova,klmitch/nova,zhimin711/nova,hanlind/nova,phenoxim/nova,cloudbase/nova,CEG-FYP-OpenStack/scheduler,gooddata/openstack-nova,NeCTAR-RC/nova,CEG-FYP-OpenStack/scheduler,cernops/nova,mikalstill/nova,mahak/nova,jianghuaw/nova,mikalstill/nova,hanlind/nova,NeCTAR-RC/nova,rajalokan/nova,Juniper/nova,BeyondTheClouds/nova,klmitch/nova,mikalstill/nova,BeyondTheClouds/nova,jianghuaw/nova,rahulunair/nova,mahak/nova,cloudbase/nova,jianghuaw/nova,bigswitch/nova,hanlind/nova,vmturbo/nova,cernops/nova,rajalokan/nova,cyx1231st/nova,rahulunair/nova,rajalokan/nova,openstack/nova,zhimin711/nova,vmturbo/nova,bigswitch/nova,openstack/nova,dims/nova,Juniper/nova,vmturbo/nova,sebrandon1/nova,sebrandon1/nova,mahak/nova,phenoxim/nova,gooddata/openstack-nova,alaski/nova,openstack/nova,BeyondTheClouds/nova,gooddata/openstack-nova