ENCODING: Incline Encoding
RFC 5545, 3.2.7, page 18
Specify an alternate inline encoding for the property value.
Values can be "8BIT" text encoding defined in [RFC2045]
"BASE64" binary encoding format defined in [RFC4648]
If the value type parameter is ";VALUE=BINARY", then the inline
encoding parameter MUST be specified with the value" ;ENCODING=BASE64".