* docs: elaborate on supported remote backend versions
This PR adds a few lines to the docs to indicate which commands are
supported by what version of the remote backend and it makes a
recommendation about which version to use.
* Clarify remote state storage w/ TFE [skip ci]
Specifically, that this is the backend to use with remote state (all
tiers) and Free-Tier vs. Enterprise tiers differ in remote operations
* website: Arrange remote backend info differently
Sander van Harmelen