FES Datepicker style improvement suggestion

[arraypress]

Since we are overriding styles, I noticed the date picker looks somewhat out of place. Additionally when the field isn't in focus/active, it just looks like a standard text field with nothing indicating it's a date selector.

I suggest we drop the control styling and come up with a more minimal and better looking date picker to match the theme.

[rubengc]

I suggest to add a jquery ui theme to match with themedd style (and configuration)

Because there are more plugins like EDD Account Tabs using jquery ui components

[rubengc]

Also, I do not know why fes provide jquery ui full style when this library provides you two css files (one with structure and the other with the default theme)