Zotero menu in the Ribbon

This update moves the Zotero icons to the Reference Ribbon for Word 2007, Word 2010 and Word 2013.

The Insert and Edit citation are bigger and merged to a dynamic icon that changes automatically if the cursor is in an existing citation or not.
The Insert and Edit Bibliography are also merged to a dynamic icon. The other icons are unchanged.

The ribbon and macro are in a new Zotero.dotm file. The existing Zotero.dot file is kept for compatibility with Word 2003 and older. The installation code checks if Word 2007 or more recent is present and copies the appropriate file.