Add support for nullable dates in filterable properties

[matt-tolliday-iss]

Would be great if DateTime? were treated as regular DateTime for the "from-to" date pickers in the .addFitlerableProperty() methods.

Currently a DateTime? is represented as a textbox

[mattbrailsford]

Good spot. Definitely should. Will sort out tomorrow 👍🏻

[mattbrailsford]

This has now been resolved and will be available for testing on the unstable feed shortly (v1.1.1-betaXXXX)