Quoted-printable Encode ignores file encoding

[Hugo-KTM]

To reproduce:

1. New File
2. Encoding --> ISO 8859-1
3. Enter Test String: "TEST=ÖÄÜ" and select text
4. MIME Tools - Quoted-printable Encode

Result:
"TEST=3D=C3=96=C3=84=C3=9C"
note: utf-8 encoded

Expected Result (ISO 8859-1 encoded):
"TEST=3D=D6=C4=DC"