Fix for #1313 and #1332

Add TEXTPLAIN in HttpHeaders
Remove all coding/decoding Attribute using URL scheme for name and
attribute
Add text/plain to contant-type
Fix for #1313 & #1332

For issue #1313, partial fix: enhance coding/deconding to missing part.
Now filename is correctly undecoded. Name and Value must be encoded to
allow parsing.
For issue #1332, add text/plain to content-type as default type if not
specified.