Add a flag to switch from http to ssh

[aloisdg]

reading list:

• Question: SSH Support libgit2/libgit2sharp#1422 <-- mostly
• https://github.com/libgit2/libgit2sharp/blob/df3b22a754ef56da8d7e3c330ce2d783c2b7982e/LibGit2Sharp.Tests/CloneFixture.cs#L19
• https://stackoverflow.com/questions/40700154/clone-a-git-repository-with-ssh-and-libgit2sharp

[aloisdg]

I think the solution is going to get rid of libgit2sharp for now, and to clone from a native shell: Call bash or posh from a fsx

I started something but it doesnt work as expected for now. Here is the branch feel free to continue or ignore it and go your own way :)