Improve suspicious character detection

Now it will print just the part of the metadata value that contains
the suspicious character (up to 80 characters, so we don't make the
line break on terminals that use 80 character width by default).

Also, print the name of the field in which the metadata value is so
that it is easier for the user to locate.

csv_metadata_quality/app.py

@@ -48,7 +48,7 @@ def run(argv):
         df[column] = df[column].apply(check.separators)
 
         # Check: suspicious characters
-        df[column] = df[column].apply(check.suspicious_characters)
+        df[column] = df[column].apply(check.suspicious_characters, field_name=column)
 
         # Fix: invalid multi-value separator
         if args.unsafe_fixes: