if passed files, clean options to git-secret hide should only delete the corresponding files

[joshrabinowitz]

When looking into #833, I discovered that

• git-secret-hide -c file.txt will remove all encrypted version of hidden files, even though filename specified - this should be fixed. Edit: my take is it should operate like this: if file.txt doesn't exist, or encryption fails, issue a warning or error (depending on -F option being enabled or not) and don't try to remove the encrypted version

• git-secret-hide -d file.txt will remove all unencrypted versions of hidden files after encryption, even though filename specified - this should be fixed. Edit: if file.txt doesn't exist do we remove the encrypted version?

• git-secret-remove -c file.txt (the other function with a -c 'clean' option) works as expected; the -c (clean) option only deleted passed files - this operates as expected

[joshrabinowitz]

@sobolevn maybe you would like to chime in with details of how you think delete and clean options should work with hide in corner cases