Unicode Error Should Not Implicitly Lead to Mumble

[domenukk]

As previously discussed in the python lib, unicode decode errors should be explicitly handled by checker authors, see:
enowars/enochecker#77

Currently, a decode error would result in Mumble, which is not correct in many situations (for example, if a field stores unprocessed data that can be placed by other teams).
I think this From should therefore go:

enochecker-rs/src/lib.rs

Line 25 in b02dace

impl From<FromUtf8Error> for CheckerError {

[domenukk]

The only benefit the Rust implementation has over python is that one must explicitly call ? on the decode - however I am not sure that service authors will correctly use this power.