Hosting should take in hosting file name as an argument

[rustd]

This would allow us to do the following.

    "web": "Microsoft.AspNet.Hosting --config hosting.ini",

The code that needs to be changed is https://github.com/aspnet/Hosting/blob/5b851c49a337e49001ed2351253ab0f52b696040/src/Microsoft.AspNet.Hosting/Program.cs

As a stretch it would be awesome if the hosting could read a json file so we could have hosting.json

[rustd]

@muratg @Eilon This is for Beta5 from the templates review

[muratg]

#277

[davidfowl]

@lodejard

[muratg]

@rustd Template change for the web command should be unblocked now.