cwltool 3.0.20200317203547: Conditionals, abstract operations, v1.2-dev2 and more!

Conditionals! #1222 @tetron
abstract operation #1255 @tetron
Use non-flat badges with the commonwl icon for conformance badges #1244 @tom-tan
Add doc field message to the output of --help #1248 @tom-tan
docker: change from --volume to --mount #1251 @mccalluc
explain who provides cwltool #1245 @mr-c
Update fragments in index #1256 @tetron
Ensure pack() produces original documents, not internally updated #1259 @tetron
Add test for packing a fragment of a document & fix. #1261 @tetron
Bump to 1.2.0-dev2 #1262 @tetron