remove avm use prompt, and insist on user installing a version if it's not yet installed

[SvenDowideit]

Closes #1562

replaces #1558

[paul-schaaf]

LGTM. pls add a line to the breaking section of the changelog

[SvenDowideit]

root@4e25ea78ccf3:/# avm use 0.22.1
Error: Could not parse version file: unexpected end of input while parsing major version number
root@4e25ea78ccf3:/# avm use latest
Error: Could not parse version file: unexpected end of input while parsing major version number

I guess there's something else i need to learn about in the code :)

(oh, this happens when there's no version installed, and the code currently tries and fails to parse nothing)

[SvenDowideit]

ok, added a fix for the initial condition

[paul-schaaf]

thank you!

[SvenDowideit]

oops, sorry for the dependency :)