Dashboard config

Hi again,

Here comes another pull request. This change concerns the dashboard and adds further option to customize it. The customization consists of the ability to add parameters from the unit to be fetched and displayed in a separate fieldset in on the dashboard. By default I have added the "Device GUI" field which is also available on the Unit Configuration page. The customization is done in the web.properties file.

Similarly to how the "Device GUI" field is fetched on the Unit Configuration page, any references to other parameters which are fetched form one parameter will be resolved to the referenced parameter. This is only possible in one iteration meaning that any references found when trying to resolve the first reference will be left unresolved. The syntax from the Unit Configuration page is reused -> ${<parameter>}.

The reason we have added this is functionality is the way the dashboard is useful to our customer. The Unit Configuration page contains many parameters and can be slow to load. On the dashboard they get a quick access overview of the unit but may still often need one or two of the parameters from the Unit Config page. This way commonly used parameters can be added to the dashboard and the workflow can be quickened.

What do you think?

Best regards,
Rikard