Add install instructions

[david-martin]

• adds install instructions to the README (for installing in a vanilla openshift 3.11 cluster)
• updates some rolebindings to reference the correct namespace & serviceaccount

Verify steps

• follow install instructions
• verify everything is reconciled (have pods running similar to output below)

oc get po
NAME                                               READY     STATUS    RESTARTS   AGE
alertmanager-application-monitoring-0              2/2       Running   0          43m
application-monitoring-operator-759c888dd6-bptw2   1/1       Running   0          43m
grafana-deployment-79cf9f88c8-l47lk                1/1       Running   0          43m
grafana-operator-795567557-vk25k                   1/1       Running   0          43m
prometheus-application-monitoring-0                3/3       Running   1          43m
prometheus-operator-65cfb97489-r7cjp               1/1       Running   0          43m

[aidenkeating]

👀