Dashboard configuration enhancements

[phil.davis]

Enhancements were committed in the last day for:

1. Provide a "None" option for dashboard widget filters
   https://redmine.pfsense.org/issues/7318

On many dashboard widgets you can select which rows of data to display, e.g. which interfaces, which gateways, which items of System Information, etc. That selection panel is opened by clicking the "wrench tool" on the widget. It already had and "All" button which would select all items with 1 click. Now if all items are selected, that changes to a "None" button, allowing you to un-select all items with 1 click. That should be handy for cases where there are a lot of items (e.g. if you have 50 interfaces) and just want to select a few to display. Click "None" then select the few that you want. If you already have a subset selected, then you can get back to none selected by clicking "All" then "None" becomes available and you can click "None" to un-select everything.

As part of this, the Traffic Graphs widget selection has been changed to a checkbox list like the other widgets (it was a multi-select box). Upgrade code should preserve previous selections.

2. Allow multiple copies of each widget on the dashboard
   https://redmine.pfsense.org/issues/7182

The first objective was to allow the content of the System Information widget to be broken up into pieces (since it has become quite long). The implementation provides a more generic way to customize our dashboard. You can add any widget multiple times, then select just the items that you want displayed in each widget copy.

e.g. You might have a lot of interfaces and a wide monitor. You could put 2 Interfaces widgets on the dashboard. Then select some interfaces in 1 copy, and other interfaces in the other copy. That way you can spread the data across columns as you wish.

Or you can put multiple picture widgets with different pictures (put the in-laws down the bottom off the screen:) - why you would really want to do this, I do not know.

Or have multiple RSS widgets with different feeds.

Or display the OpenVPN servers in 1 column, and OpenVPN clients in the other.

Or… - do as you wish.

What has not happened yet:
a) The traffic graphs widget does not have code to run multiple copies properly. For the moment, do not add multiple traffic graphs widgets (I will work on that - the traffic graphs widget code has a bunch of global variable stuff that needs an extra level of abstraction...)

b) The old widget preference settings are not migrated to the new scheme. So you will find that some dashboard widget preferences will need to be selected again.  (I will do upgrade code for this "real soon now")

Have a play and report back.