Release v0.8

This release includes the following changes:

• add an env resource type for setting environment variables
• add a job:capture(VARIABLE) action to job tasks for capturing the stdout of a job in a variable
• add port, user, and devices fields to the job resource
• add dobi autoclean built-in task for running the remove action on all resources
• add user. variable support for getting uid, username, etc
• fixed a bug with image authentication on private registries

See milestone 0.8 for a full list of issues and PRs.

Thanks @cescoferraro for your contributions to this release!