Fixed Insert Link URLs and child modals resetting modal forms

- Fixed an issue where launching the Insert Link or Delete child modals from an edit form were refreshing the edit form's data upon closing.
- Added a usability tweak for Insert Link: Whenever the user pastes a URL, depending how they pasted it, the default "http://" might still prefix the URL. This removes the first "http://" if multiple prefixes are detected (i.e. "http://https://sites.google.com/...").