Add --print-supported-versions option that prints supported CWL versions

[tom-tan]

Currently the only way to check whether the certain version of CWL file is supported by cwltool is to run cwltool with CWL files and to check its output.

This request adds --print-supported-versions that prints supported CWL versions.
We can check the CWL versions supported by cwltool by using this option.

Here is the output of --print-supported-versions option:

$ ./cwltool.py --print-supported-versions
./cwltool.py 1.0.20170516234254
draft-2
draft-3
draft-3.dev1
draft-3.dev2
draft-3.dev3
draft-3.dev4
draft-3.dev5
draft-4.dev1
draft-4.dev2
draft-4.dev3
v1.0
v1.0.dev4
v1.1.0-dev1

[cwl-bot]

Can one of the admins verify this patch?

[mr-c]

Jenkins, okay to test

[mr-c]

Thank you @tom-tan for this PR!
FYI, many of those versions require the --enable-dev flag -- perhaps it would be best to only print the full list if --enable-dev was also passed?

[tom-tan]

Thank you for your advice.

I will update this PR to take it into account.

[tom-tan]

Done!

I update supportedCWLversions to take enable_dev flag.

• If enable_dev is true, it returns all supported CWL versions (include devel versions).
• Otherwise it returns all draft and released versions without devel versions.

[mr-c]

Great, thanks again!