Extra null check when initialising Url picker

If a property already exists with a value, after changing it's type to the Url Picker, the value object may not be in a format the Url Picker knows about. For example, changing a property from a Content Picker to a Url Picker.
Extra init check to make sure value has the correct type

Along with issue #10, a valid Url Picker value must have a type object. If a property has been converted and has a value, the value object may not be in the correct format. To fix, look to see if we have a type object in the value object. If not, initialise as new.
Amend newWindow default to false

This is probably personal preference but I think the default value for opening a link in a window should be false.
Merge branch 'pr/10' into develop
Merge branch 'pr/11' into develop

Conflicts:
	urlpicker/app/scripts/controllers/url.picker.controller.js
Allow for hiding of tabs

- default to content