SystemsLab 0.0.60

Fixed

• Errors which use with_not_found_error will now contain their actual source locations instead of a location within the systemslab-error crate.
• The agent can now accept submit requests that don't contain the metadata field. This fixes an issue where it is no longer possible to submit tasks when using a server running v0.0.58 and an agent running v0.0.59.