Rename projName to projectName in apitype.Stack

This value was never used before, but it had a shorter name. In other
API Types we are using `projectName` which we all prefer. Since we are
going to start using this value going forward, let's adopt the good
name now when it won't break anyone.

pkg/apitype/core.go

@@ -261,7 +261,7 @@ type Stack struct {
 	OrgName   string `json:"orgName"`
 
 	RepoName    string       `json:"repoName"`
-	ProjectName string       `json:"projName"`
+	ProjectName string       `json:"projectName"`
 	StackName   tokens.QName `json:"stackName"`
 
 	ActiveUpdate string                  `json:"activeUpdate"`