[fix] Now decodeMimeStr function will decode MIME string only if contains charset info and this charset is different from target one.
 Also mb_convert_encoding is being used now instead of iconv, as the latter works badly on corrupted input
minor changes:
- trimming "From" header
- using accessors for properties
[fixed] RFC2231 Parameter value continuations is now supported.
These take place for a long attachment filenames.
See http://tools.ietf.org/html/rfc2231#section-3
fixed disposition check
[fixed] RFC2231 Parameter value extended encoding is now supported.
Faced that case with attachment with long name in Russian - got filename parameter encoded as per RFC2231 Section 4
See http://tools.ietf.org/html/rfc2231#section-4