dom-checkbox plugin conflicts with datetime-moment

If you have the datetime-moment plugin loaded and add a moment type the dom-checkbox plugin (and maybe others) will not work properly anymore.

This is caused by the dom-monent plugin also accepting empty strings (or strings only consisting of HTML tags) as valid dates and therefor assigning a moment date type to the column. The custom data from the dom-checkbox plugin can then not be sorted anymore, because it is not a valid date format.

I see two possible fixes:

• don't detect empty strings as dates
• do the format detection on the output of the custom data source plugin.

Start by reading the dom-checkbox, datetime-moment, and dom-moment plugin implementations and reproduce the conflict with empty or HTML-only values and custom checkbox data. Check how date types are detected and sorting is selected; done means the custom data remains sortable when datetime-moment and dom-checkbox are loaded together.