install behind firewalls

[doutriaux1]

libcdms and lcmor (and likely VTK) cannot be cloned from github behind some firewalls

2 possible solution:

• switch build from git to tarballs via a new option
• allow user to pass a different git protocol and base e.g: username@usermachine:user_path/libcdms.git

[durack1]

@doutriaux1 excellent, thanks for this.. @gleckler1 should be happy about making it even easier for users..