* Add command suggestions
This adds suggestions of similar commands in case users mistype a
command. Before:
```
$ spack spack
==> Error: spack is not a recognized Spack command or extension command; check with `spack commands`.
```
After:
```
$ spack spack
==> Error: spack is not a recognized Spack command or extension command; check with `spack commands`.
Did you mean one of the following commands?
spec
patch
```
* Add package name suggestions
* Remove suggestion to run spack clean -m
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