Support input/output names containing spaces

**Is this a BUG REPORT or FEATURE REQUEST?**:
FEATURE REQUEST

Currently, the input/output names cannot have spaces. I see no technical reason for that.
I'd like to be able to use input/output names with spaces.

Maybe this can be extended to template names. (Task names and workflow name probably cannot have spaces since they're used for Kubernetes resource names.)

The issue does not name files, tests, or entry points. Start by locating where input/output names are validated and where workflow templates are represented, then check the Kubernetes naming constraints mentioned in the request. Done means input and output names containing spaces work without breaking task or workflow resource naming.

Written by the indexing model from the issue text.