Feature/git fork

[hickey]

Added support for forking on instances of Github other than github.com.

In addition added ability to pull stored settings from git config so that one is not prompted each time for things like username and such.

Also introduced a self documenting way of including helper scripts into the generated scripts. See the Makefile and helper/config-value for details. Also helps keeping one from forgetting to update the needs_* files.

[hickey]

Added better detection when the fork fails (which is really a comms error with talking to Github).

If directory already exists, clone will silently fail and the upstream references will be created. If they already exist, then a warning message is printed that it exists.

[hickey]

If you would prefer, I can squash all the commits and resubmit the PR.

[hickey]

Sorry, I have been busy and this PR fell off the list. Updated wording in the documentation and surprised that I missed that typo. Thanks.

[hickey]

Let me know if you would like this PR squashed.

[adriaanzon]

You may want to use the curl's -f flag like I did in #649, instead of checking if the response contains "message"

[bl-ue]

We should close this — it's out-of-date and 4 years old, and has no votes.