Rename `xvc file checkout` to `xvc file recheck`

[Emre Sahin]

We'll use recheck as a synonym for checkout to differentiate between Git behavior.

• Cache type will be renamed to recheck type
• Any options for --cache-type will be --recheck-as
• Alias for xvc file recheck will be xvcfr.
• We can continue to use checkout as an aliased command in the root level, but xvcfc alias is better to mean xvc file copy. Maybe we can have a xvcfco for checkout.