Fixing issues with changing hub_loaded to loaded_to_hub in saved variables file

[jimmyjon711]

Major Changes in this PR

• Fixing issue where hub_loaded is not loaded_to_hub in vars file, added a backwards combability check so users can upgrade without problem
• Added an extruder object to lane so that extruder does not have to be looked up all the time
• Fixed some more places where lane.name was being used as a key
• Fixed error when trying to map lanes
• Updated SET_SPOOLID to SET_SPOOL_ID so the documentation would match the actual macro name

Notes to Code Reviewers

How the changes in this PR are tested

• Went through tool load and unload, tested mapping lanes.
• Deleted vars files to make sure they were recreated correctly
• Copied over old format of vars file to make sure configuration stayed the same between the old and new format

PR Checklist: (Checked-off items are either done or do not apply to this PR)

• I have performed a self-review of my code
• CHANGELOG.md is updated (if end-user facing)
• Sent notification to software-design channel requesting review