TinyMCE Improvements: Open links from note window with popup (similar to Google Docs) and auto-create links

Hi,

as discussed [here](https://github.com/zotero/zotero/issues/448#issuecomment-33897192), this pull request adds an inline popup for single-clicks on links to Zotero notes. The popup allows the user to open links, edit them, or remove them. This behavior is similar to Google Docs and Apple Pages and allows the user to open links directly from Zotero notes (for discussion about this see [here](https://forums.zotero.org/discussion/25832/note-hyperlinks-in-standalone/), [here](https://groups.google.com/forum/#!searchin/zotero-dev/uri/zotero-dev/7XIhuSBFOOI/_6z7o0G4YfcJ), and [here](https://forums.zotero.org/discussion/26314/trigger-the-hyperlink-in-the-tinymce-editor/)). The `open link` button also appears when the user right-clicks on a link together with the previous options. Opening the link is handled through `ZoteroPane.loadURI`.

In addition, the pull request adds the TinyMCE 3 plugin [autolink](www.tinymce.com/wiki.php/Plugin3x:autolink‎) to Zotero. This plugin automatically creates links when the user types `www.nytimes.com`.