Centralize errors originating in CLI

[victor-linroth-sensmetry]

Currently the sysand crate is littered with bail! and anyhow! macros used to generate ad hoc errors in place. It would be nice to try to centralize these in the CliError enum, partly to reduce duplication of error messages and partly to get a better overview of the errors originating in the CLI.

Note that bail! is still useful for simplifying the control flow of error handling but it could preferably be bail!(CliError::<...>) instead of bail!("<ad hoc message>").

[victor-linroth-sensmetry]

Finalizing this issue should probably wait for #149 to get merged, but some of the work can probably get started with before.