Popup service: Adding destroy function and compile/link in constructor

This pull request

- Added a destroy function to explicitly destroy the dialog (remove html element and scope)
- Separates destruction and closing of popups.
- A new option parameter `destroyOnClose` (default is true) to specify if to destroy the dialog on close
- Move compile/link phase to constructor
- Open only shows the dialog, Close hides dialog

Default behavior does not change at all. We'll have a little more flexibility with the popup service.