Password visibility toggle

Allows users to toggle the visibility of any passwords they have allowed google chrome to store for them by adding an item to the context menu. Users can right click on INPUT fields that have been obfuscated and select the "show password" option from the context menu. The password can be hidden again by right clicking the password field and choosing "hide password". That's it! This is a very simple extension and the code is up on github if you want to view it.