Sentence cased text everywhere (#3166)

* Sentence cased text everywhere

Follows Weave Cloud's direction of sentence case on most things.

* More space between sorter caret and label

* Use full topology name for table header

render/detailed/node.go

@@ -181,7 +181,7 @@ var nodeSummaryGroupSpecs = []struct {
 	{
 		topologyID: report.ContainerImage,
 		NodeSummaryGroup: NodeSummaryGroup{
-			Label:   "Container Images",
+			Label:   "Container images",
 			Columns: []Column{},
 		},
 	},

render/detailed/node_test.go

@@ -65,7 +65,7 @@ func TestMakeDetailedHostNode(t *testing.T) {
 				},
 				{
 					ID:       "local_networks",
-					Label:    "Local Networks",
+					Label:    "Local networks",
 					Value:    "10.10.10.0/24",
 					Priority: 13,
 				},
@@ -129,7 +129,7 @@ func TestMakeDetailedHostNode(t *testing.T) {
 				Nodes: []detailed.NodeSummary{process1NodeSummary, process2NodeSummary},
 			},
 			{
-				Label:      "Container Images",
+				Label:      "Container images",
 				TopologyID: "containers-by-image",
 				Columns:    []detailed.Column{},
 				Nodes:      []detailed.NodeSummary{containerImageNodeSummary},

render/detailed/summary_test.go

@@ -429,13 +429,13 @@ func TestNodeTables(t *testing.T) {
 				{
 					ID:    docker.EnvPrefix,
 					Type:  report.PropertyListType,
-					Label: "Environment Variables",
+					Label: "Environment variables",
 					Rows:  []report.Row{},
 				},
 				{
 					ID:    docker.LabelPrefix,
 					Type:  report.PropertyListType,
-					Label: "Docker Labels",
+					Label: "Docker labels",
 					Rows: []report.Row{
 						{
 							ID: "label_label1",