added codeplex issues page

Let's get organised! I created a page where we can put all the codeplex issues we are tracking. 

For now I did a quick sweep of my own codeplex issues and some I knew in the DT repos. I'm not sure about the structure, so I went with something simple.

@basarat @johnnyreilly @vvakame I think you guys have some stuff for this too. Everyone else is welcome too.

First one who thinks this is cool and wants to add something can merge it.

Let bundle it up and slap the compiler team with it :sunglasses: