Support k-folds for Actions-based skills

[andrewrfreed]

There are some APIs for working with skills in the v2 API - https://cloud.ibm.com/apidocs/assistant-v2#importskills - they are in a different API path than in Dialog skills.

Need to investigate these APIs, ideally the k-folds functionality can point to correct API for workspace (v1) or assistant (v2).

Update: There are APIs for Assistants too: https://cloud.ibm.com/apidocs/assistant-v2#createassistant

The old flow was:

• Create k temporary skills
• Train them
• Test them
• Delete them (leave no trace!)

The new flow can be:

• Create k temporary assistants and skills (1-1 link)
• Train them
• Test them
• Delete them (leave no trace!)

This should fit with the existing paradigm.