Allow Cassandra NodePools to be configured with resource requests and limits.

[wallrj]

• Added a CassandraClusterNodePoolSpec.Resources field, bringing it in line with ElasticSearchCluster.
• Pass the resources through to the nodepool pods.
• Added quotas to all the namespaces in E2E tests, to ensure that tests fail if there Navigator creates pods without resource requests.
• Short description of NodePool resource requests and limits.
• Fixed a problem where a helm-installed Navigator controller would attempt to create leader election events in kube-system rather than in the namespace of the helm release.

Fixes: #280

Release note:

NONE

[wallrj]

Added quotas to all the E2E test namespaces and now I see this warning in the events:

        {
            "name": "cass-test-ringnodes.151b7aba66078503",
            "namespace": "test-cassandra-1520944168-10788",
            "selfLink": "/api/v1/namespaces/test-cassandra-1520944168-10788/events/cass-test-ringnodes.151b7aba66078503",
            "uid": "571b5ac2-26ba-11e8-bd3d-5254002248c3",
            "resourceVersion": "3217",
            "creationTimestamp": "2018-03-13T12:30:40Z",
            "InvolvedObject": {
                "Kind": "StatefulSet",
                "Namespace": "test-cassandra-1520944168-10788",
                "Name": "cass-test-ringnodes",
                "UID": "5704c37f-26ba-11e8-bd3d-5254002248c3",
                "APIVersion": "apps",
                "ResourceVersion": "1114",
                "FieldPath": ""
            },
            "Reason": "FailedCreate",
            "Message": "create Pod cass-test-ringnodes-0 in StatefulSet cass-test-ringnodes failed error: pods \"cass-test-ringnodes-0\" is forbidden: failed quota: navigator-test-quota: must specify cpu,memory",
            "Source": {
                "Component": "statefulset",
                "Host": ""
            },
            "FirstTimestamp": "2018-03-13T12:30:40Z",
            "LastTimestamp": "2018-03-13T12:50:16Z",
            "Count": 55,
            "Type": "Warning"
        },

So let's try fixing that...

[wallrj]

/retest

[munnerz]

/lgtm /approve

[jetstack-bot]

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This pull-request has been approved by: munnerz

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[jetstack-ci-bot]

/test all [submit-queue is verifying that this PR is safe to merge]

[jetstack-ci-bot]

Automatic merge from submit-queue.