Adding Dockerfile for dotnet

[trumhemcut]

I've just created a new image for dotnet coreclr, basically it was created from https://github.com/aspnet/aspnet-docker/blob/master/1.0.0-rc1-update1-coreclr/Dockerfile (size 357.7 MB compare with this one 69.58 MB, a significant number smaller than standard image of Microsoft) and we can run a very basic HelloWorld app.

But there're many packages I've ignored since they are not available on Alpine:

1. libcurl3-gnutls
2. sqlite3
3. libsqlite3-dev
4. libunwind8
5. libicu-dev
6. zlib1g

Thanks,
Phi

[treeder]

Thanks! I assume this is different than the mono image we have?

[trumhemcut]

@treeder Yes, it's only Alpine with the dotnet coreclr since dotnet can run on Linux without based on Mono. As a result, we can shrink down the size really much.

[treeder]

Can you make a README for this like the rest of images.

[gerektoolhy]

@trumhemcut , this is awesome!

[treeder]

Still need a README for this. Also, should there be a :dev version?

[darkSasori]

DNX is an outdate version of coreclr