make SSH checkout the default

[keckelt]

Hi,

GitHub removed support of cloning repositories with https / github credentials. See https://github.blog/2020-12-15-token-authentication-requirements-for-git-operations/

Clone operations of private repos will fail with the following error:

remote: Support for password authentication was removed on August 13, 2021. Please use a personal access token instead.
remote: Please see https://github.blog/2020-12-15-token-authentication-requirements-for-git-operations/ for more information.
fatal: Authentication failed for 'https://github.com/Caleydo/cohort_product.git/'

I therefore suggest to use SSH as the default for setting up workspaces and in the build.js script.