Reintroduces an Instructions only tab to the TM2 project page for mappers

This PR fixes #193 And re-introduces an instructions only tab by creating a Description tab, removes the description text from the Instructions tab and puts it on the new Description tab. It also adds a button at the bottom of the Description text to take the user to the Instructions tab. The button text is: "Instructions and Start Contributing" There are pictures on issue #193 showing how the two affected panels look.

I felt this was the very cleanest way to add in a Description tab and make it a full class tab citizen in the application.