Improve diagnostic highlighting and codes

[garrytrinder]

• highlight plugin property only
• Add code for plugin check

• invalidConfigSection, highlight key property only

• Add information warning to urlsToWatch if empty

• highlight name value
• add code for reporter check

• highlight name value
• add code for execution summary check

• highlight plugin property only
• add code for one enabled plugin check

• highlight name value
• add code for apicenter check